diff --git a/src/error.h b/src/error.h
index 366bcd3ade..206bb67fbd 100644
--- a/src/error.h
+++ b/src/error.h
@@ -24,5 +24,7 @@ enum WarningLevel {
 
 void ShowErrorMessage(StringID summary_msg, StringID detailed_msg, WarningLevel wl, int x = 0, int y = 0, uint textref_stack_size = 0, const uint32 *textref_stack = NULL);
 void ClearErrorMessages();
+void ShowFirstError();
+void UnshowCriticalError();
 
 #endif /* ERROR_H */
diff --git a/src/error_gui.cpp b/src/error_gui.cpp
index ee2d5325a1..72e051281c 100644
--- a/src/error_gui.cpp
+++ b/src/error_gui.cpp
@@ -127,6 +127,8 @@ public:
 typedef std::list<ErrorMessageData> ErrorList;
 /** The actual queue with errors. */
 ErrorList _errors;
+/** Whether the window system is initialized or not. */
+bool _window_system_initialized = false;
 
 /** Window class for displaying an error message window. */
 struct ErrmsgWindow : public Window, ErrorMessageData {
@@ -261,11 +263,7 @@ public:
 	~ErrmsgWindow()
 	{
 		SetRedErrorSquare(INVALID_TILE);
-
-		if (!_errors.empty()) {
-			new ErrmsgWindow(_errors.front());
-			_errors.pop_front();
-		}
+		if (_window_system_initialized) ShowFirstError();
 	}
 
 	virtual EventState OnKeyPress(uint16 key, uint16 keycode)
@@ -293,6 +291,30 @@ void ClearErrorMessages()
 	_errors.clear();
 }
 
+/** Show the first error of the queue. */
+void ShowFirstError()
+{
+	_window_system_initialized = true;
+	if (!_errors.empty()) {
+		new ErrmsgWindow(_errors.front());
+		_errors.pop_front();
+	}
+}
+
+/**
+ * Unshow the critical error. This has to happen when a critical
+ * error is shown and we uninitialise the window system, i.e.
+ * remove all the windows.
+ */
+void UnshowCriticalError()
+{
+	ErrmsgWindow *w = (ErrmsgWindow*)FindWindowById(WC_ERRMSG, 0);
+	if (w != NULL) {
+		if (w->IsCritical()) _errors.push_front(*w);
+		_window_system_initialized = false;
+	}
+}
+
 /**
  * Display an error message in a window.
  * @param summary_msg  General error message showed in first line. Must be valid.
diff --git a/src/network/core/tcp_game.cpp b/src/network/core/tcp_game.cpp
index 4f0202c602..64b7ba97a8 100644
--- a/src/network/core/tcp_game.cpp
+++ b/src/network/core/tcp_game.cpp
@@ -18,6 +18,7 @@
 #include "../network.h"
 #include "../network_internal.h"
 #include "../../debug.h"
+#include "../../error.h"
 
 #include "table/strings.h"
 
@@ -46,8 +47,7 @@ NetworkRecvStatus NetworkGameSocketHandler::CloseConnection(bool error)
 	if (!_network_server && _networking) {
 		_switch_mode = SM_MENU;
 		_networking = false;
-		extern StringID _switch_mode_errorstr;
-		_switch_mode_errorstr = STR_NETWORK_ERROR_LOSTCONNECTION;
+		ShowErrorMessage(STR_NETWORK_ERROR_LOSTCONNECTION, INVALID_STRING_ID, WL_CRITICAL);
 
 		return NETWORK_RECV_STATUS_CONN_LOST;
 	}
diff --git a/src/network/network.cpp b/src/network/network.cpp
index 0b6e9c35a8..dd47be1729 100644
--- a/src/network/network.cpp
+++ b/src/network/network.cpp
@@ -36,6 +36,7 @@
 #include "../rev.h"
 #include "../core/pool_func.hpp"
 #include "../gfx_func.h"
+#include "../error.h"
 #include "table/strings.h"
 
 #ifdef DEBUG_DUMP_COMMANDS
@@ -287,8 +288,7 @@ uint NetworkCalculateLag(const NetworkClientSocket *cs)
 void NetworkError(StringID error_string)
 {
 	_switch_mode = SM_MENU;
-	extern StringID _switch_mode_errorstr;
-	_switch_mode_errorstr = error_string;
+	ShowErrorMessage(error_string, INVALID_STRING_ID, WL_CRITICAL);
 }
 
 /**
diff --git a/src/network/network_client.cpp b/src/network/network_client.cpp
index c982536489..fd133dc548 100644
--- a/src/network/network_client.cpp
+++ b/src/network/network_client.cpp
@@ -526,12 +526,11 @@ bool ClientNetworkGameSocketHandler::IsConnected()
  ************/
 
 extern bool SafeLoad(const char *filename, int mode, GameMode newgm, Subdirectory subdir, struct LoadFilter *lf = NULL);
-extern StringID _switch_mode_errorstr;
 
 NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_FULL(Packet *p)
 {
 	/* We try to join a server which is full */
-	_switch_mode_errorstr = STR_NETWORK_ERROR_SERVER_FULL;
+	ShowErrorMessage(STR_NETWORK_ERROR_SERVER_FULL, INVALID_STRING_ID, WL_CRITICAL);
 	DeleteWindowById(WC_NETWORK_STATUS_WINDOW, 0);
 
 	return NETWORK_RECV_STATUS_SERVER_FULL;
@@ -540,7 +539,7 @@ NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_FULL(Packet *p)
 NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_BANNED(Packet *p)
 {
 	/* We try to join a server where we are banned */
-	_switch_mode_errorstr = STR_NETWORK_ERROR_SERVER_BANNED;
+	ShowErrorMessage(STR_NETWORK_ERROR_SERVER_BANNED, INVALID_STRING_ID, WL_CRITICAL);
 	DeleteWindowById(WC_NETWORK_STATUS_WINDOW, 0);
 
 	return NETWORK_RECV_STATUS_SERVER_BANNED;
@@ -652,28 +651,28 @@ NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_ERROR(Packet *p
 		case NETWORK_ERROR_NOT_AUTHORIZED:
 		case NETWORK_ERROR_NOT_EXPECTED:
 		case NETWORK_ERROR_COMPANY_MISMATCH:
-			_switch_mode_errorstr = STR_NETWORK_ERROR_SERVER_ERROR;
+			ShowErrorMessage(STR_NETWORK_ERROR_SERVER_ERROR, INVALID_STRING_ID, WL_CRITICAL);
 			break;
 		case NETWORK_ERROR_FULL:
-			_switch_mode_errorstr = STR_NETWORK_ERROR_SERVER_FULL;
+			ShowErrorMessage(STR_NETWORK_ERROR_SERVER_FULL, INVALID_STRING_ID, WL_CRITICAL);
 			break;
 		case NETWORK_ERROR_WRONG_REVISION:
-			_switch_mode_errorstr = STR_NETWORK_ERROR_WRONG_REVISION;
+			ShowErrorMessage(STR_NETWORK_ERROR_WRONG_REVISION, INVALID_STRING_ID, WL_CRITICAL);
 			break;
 		case NETWORK_ERROR_WRONG_PASSWORD:
-			_switch_mode_errorstr = STR_NETWORK_ERROR_WRONG_PASSWORD;
+			ShowErrorMessage(STR_NETWORK_ERROR_WRONG_PASSWORD, INVALID_STRING_ID, WL_CRITICAL);
 			break;
 		case NETWORK_ERROR_KICKED:
-			_switch_mode_errorstr = STR_NETWORK_ERROR_KICKED;
+			ShowErrorMessage(STR_NETWORK_ERROR_KICKED, INVALID_STRING_ID, WL_CRITICAL);
 			break;
 		case NETWORK_ERROR_CHEATER:
-			_switch_mode_errorstr = STR_NETWORK_ERROR_CHEATER;
+			ShowErrorMessage(STR_NETWORK_ERROR_CHEATER, INVALID_STRING_ID, WL_CRITICAL);
 			break;
 		case NETWORK_ERROR_TOO_MANY_COMMANDS:
-			_switch_mode_errorstr = STR_NETWORK_ERROR_TOO_MANY_COMMANDS;
+			ShowErrorMessage(STR_NETWORK_ERROR_TOO_MANY_COMMANDS, INVALID_STRING_ID, WL_CRITICAL);
 			break;
 		default:
-			_switch_mode_errorstr = STR_NETWORK_ERROR_LOSTCONNECTION;
+			ShowErrorMessage(STR_NETWORK_ERROR_LOSTCONNECTION, INVALID_STRING_ID, WL_CRITICAL);
 	}
 
 	DeleteWindowById(WC_NETWORK_STATUS_WINDOW, 0);
@@ -710,7 +709,7 @@ NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_CHECK_NEWGRFS(P
 	}
 
 	/* NewGRF mismatch, bail out */
-	_switch_mode_errorstr = STR_NETWORK_ERROR_NEWGRF_MISMATCH;
+	ShowErrorMessage(STR_NETWORK_ERROR_NEWGRF_MISMATCH, INVALID_STRING_ID, WL_CRITICAL);
 	return ret;
 }
 
@@ -849,7 +848,7 @@ NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_MAP_DONE(Packet
 
 	if (!load_success) {
 		DeleteWindowById(WC_NETWORK_STATUS_WINDOW, 0);
-		_switch_mode_errorstr = STR_NETWORK_ERROR_SAVEGAMEERROR;
+		ShowErrorMessage(STR_NETWORK_ERROR_SAVEGAMEERROR, INVALID_STRING_ID, WL_CRITICAL);
 		return NETWORK_RECV_STATUS_SAVEGAME;
 	}
 	/* If the savegame has successfully loaded, ALL windows have been removed,
@@ -1053,7 +1052,7 @@ NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_SHUTDOWN(Packet
 	/* Only when we're trying to join we really
 	 * care about the server shutting down. */
 	if (this->status >= STATUS_JOIN) {
-		_switch_mode_errorstr = STR_NETWORK_MESSAGE_SERVER_SHUTDOWN;
+		ShowErrorMessage(STR_NETWORK_MESSAGE_SERVER_SHUTDOWN, INVALID_STRING_ID, WL_CRITICAL);
 	}
 
 	return NETWORK_RECV_STATUS_SERVER_ERROR;
@@ -1068,7 +1067,7 @@ NetworkRecvStatus ClientNetworkGameSocketHandler::Receive_SERVER_NEWGAME(Packet
 		 * Client ID modulo 16. This way reconnects should be spread
 		 * out a bit. */
 		_network_reconnect = _network_own_client_id % 16;
-		_switch_mode_errorstr = STR_NETWORK_MESSAGE_SERVER_REBOOT;
+		ShowErrorMessage(STR_NETWORK_MESSAGE_SERVER_REBOOT, INVALID_STRING_ID, WL_CRITICAL);
 	}
 
 	return NETWORK_RECV_STATUS_SERVER_ERROR;
@@ -1157,7 +1156,7 @@ void ClientNetworkGameSocketHandler::CheckConnection()
 	 * the server will forcefully disconnect you. */
 	if (lag > 20) {
 		this->NetworkGameSocketHandler::CloseConnection();
-		_switch_mode_errorstr = STR_NETWORK_ERROR_LOSTCONNECTION;
+		ShowErrorMessage(STR_NETWORK_ERROR_LOSTCONNECTION, INVALID_STRING_ID, WL_CRITICAL);
 		return;
 	}
 
diff --git a/src/openttd.cpp b/src/openttd.cpp
index 464330581a..a902d197d6 100644
--- a/src/openttd.cpp
+++ b/src/openttd.cpp
@@ -71,9 +71,6 @@
 
 #include "table/strings.h"
 
-/** Error message to show when switching modes. */
-StringID _switch_mode_errorstr;
-
 void CallLandscapeTick();
 void IncreaseDate();
 void DoPaletteAnimations();
@@ -524,7 +521,6 @@ int ttd_main(int argc, char *argv[])
 
 	_game_mode = GM_MENU;
 	_switch_mode = SM_MENU;
-	_switch_mode_errorstr = INVALID_STRING_ID;
 	_config_file = NULL;
 
 	GetOptData mgo(argc - 1, argv + 1, _options);
@@ -1103,11 +1099,6 @@ void SwitchToMode(SwitchMode new_mode)
 
 		default: NOT_REACHED();
 	}
-
-	if (_switch_mode_errorstr != INVALID_STRING_ID) {
-		ShowErrorMessage(_switch_mode_errorstr, INVALID_STRING_ID, WL_CRITICAL);
-		_switch_mode_errorstr = INVALID_STRING_ID;
-	}
 }
 
 
diff --git a/src/saveload/afterload.cpp b/src/saveload/afterload.cpp
index 3873b5d6ed..85a1ace1da 100644
--- a/src/saveload/afterload.cpp
+++ b/src/saveload/afterload.cpp
@@ -53,6 +53,7 @@
 #include "../smallmap_gui.h"
 #include "../news_func.h"
 #include "../group.h"
+#include "../error.h"
 
 #include "table/strings.h"
 
@@ -60,7 +61,6 @@
 
 #include <signal.h>
 
-extern StringID _switch_mode_errorstr;
 extern Company *DoStartupNewCompany(bool is_ai, CompanyID company = INVALID_COMPANY);
 
 /**
@@ -622,8 +622,8 @@ bool AfterLoadGame()
 	}
 
 	switch (gcf_res) {
-		case GLC_COMPATIBLE: _switch_mode_errorstr = STR_NEWGRF_COMPATIBLE_LOAD_WARNING; break;
-		case GLC_NOT_FOUND:  _switch_mode_errorstr = STR_NEWGRF_DISABLED_WARNING; _pause_mode = PM_PAUSED_ERROR; break;
+		case GLC_COMPATIBLE: ShowErrorMessage(STR_NEWGRF_COMPATIBLE_LOAD_WARNING, INVALID_STRING_ID, WL_CRITICAL); break;
+		case GLC_NOT_FOUND:  ShowErrorMessage(STR_NEWGRF_DISABLED_WARNING, INVALID_STRING_ID, WL_CRITICAL); _pause_mode = PM_PAUSED_ERROR; break;
 		default: break;
 	}
 
@@ -1756,9 +1756,7 @@ bool AfterLoadGame()
 		RoadVehicle *v;
 		FOR_ALL_ROADVEHICLES(v) {
 			if (v->First() == v && HasBit(EngInfo(v->engine_type)->misc_flags, EF_ROAD_TRAM)) {
-				if (_switch_mode_errorstr == INVALID_STRING_ID || _switch_mode_errorstr == STR_NEWGRF_COMPATIBLE_LOAD_WARNING) {
-					_switch_mode_errorstr = STR_WARNING_LOADGAME_REMOVED_TRAMS;
-				}
+				ShowErrorMessage(STR_WARNING_LOADGAME_REMOVED_TRAMS, INVALID_STRING_ID, WL_CRITICAL);
 				delete v;
 			}
 		}
diff --git a/src/town_cmd.cpp b/src/town_cmd.cpp
index 4413092d3f..407a837d19 100644
--- a/src/town_cmd.cpp
+++ b/src/town_cmd.cpp
@@ -1896,8 +1896,7 @@ bool GenerateTowns(TownLayout layout)
 
 	/* If there are no towns at all and we are generating new game, bail out */
 	if (Town::GetNumItems() == 0 && _game_mode != GM_EDITOR) {
-		extern StringID _switch_mode_errorstr;
-		_switch_mode_errorstr = STR_ERROR_COULD_NOT_CREATE_TOWN;
+		ShowErrorMessage(STR_ERROR_COULD_NOT_CREATE_TOWN, INVALID_STRING_ID, WL_CRITICAL);
 	}
 
 	return false;  // we are still without a town? we failed, simply
diff --git a/src/window.cpp b/src/window.cpp
index 9241f6c84e..33b48916af 100644
--- a/src/window.cpp
+++ b/src/window.cpp
@@ -32,6 +32,7 @@
 #include "hotkeys.h"
 #include "toolbar_gui.h"
 #include "statusbar_gui.h"
+#include "error.h"
 
 
 static Point _drag_delta; ///< delta between mouse cursor and upper left corner of dragged window
@@ -1448,6 +1449,8 @@ void InitWindowSystem()
 
 	NWidgetLeaf::InvalidateDimensionCache(); // Reset cached sizes of several widgets.
 	NWidgetScrollbar::InvalidateDimensionCache();
+
+	ShowFirstError();
 }
 
 /**
@@ -1455,6 +1458,8 @@ void InitWindowSystem()
  */
 void UnInitWindowSystem()
 {
+	UnshowCriticalError();
+
 	Window *w;
 	FOR_ALL_WINDOWS_FROM_FRONT(w) delete w;