Index: src/genworld.cpp
===================================================================
--- src/genworld.cpp	(revision 22846)
+++ src/genworld.cpp	(working copy)
@@ -124,7 +124,12 @@
 			ConvertGroundTilesIntoWaterTiles();
 			IncreaseGeneratingWorldProgress(GWP_OBJECT);
 		} else {
-			GenerateLandscape(_gw.mode);
+			if (!GenerateLandscape(_gw.mode)) {
+				_cur_company.Restore();
+				HandleGeneratingWorldAbortion();
+				return;
+			}
+
 			GenerateClearTile();
 
 			/* only generate towns, tree and industries in newgame mode. */
Index: src/heightmap.cpp
===================================================================
--- src/heightmap.cpp	(revision 22846)
+++ src/heightmap.cpp	(working copy)
@@ -22,6 +22,8 @@
 
 #include "table/strings.h"
 
+extern StringID _switch_mode_errorstr, _switch_mode_detailed_errorstr;
+
 /**
  * Convert RGB colours to Grayscale using 29.9% Red, 58.7% Green, 11.4% Blue
  *  (average luminosity formula) -- Dalestan
@@ -107,20 +109,23 @@
 
 	fp = FioFOpenFile(filename, "rb", HEIGHTMAP_DIR);
 	if (fp == NULL) {
-		ShowErrorMessage(STR_ERROR_PNGMAP, STR_ERROR_PNGMAP_FILE_NOT_FOUND, WL_ERROR);
+		_switch_mode_errorstr = STR_ERROR_PNGMAP;
+		_switch_mode_detailed_errorstr = STR_ERROR_PNGMAP_FILE_NOT_FOUND;
 		return false;
 	}
 
 	png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
 	if (png_ptr == NULL) {
-		ShowErrorMessage(STR_ERROR_PNGMAP, STR_ERROR_PNGMAP_MISC, WL_ERROR);
+		_switch_mode_errorstr = STR_ERROR_PNGMAP;
+		_switch_mode_detailed_errorstr = STR_ERROR_PNGMAP_MISC;
 		fclose(fp);
 		return false;
 	}
 
 	info_ptr = png_create_info_struct(png_ptr);
 	if (info_ptr == NULL || setjmp(png_jmpbuf(png_ptr))) {
-		ShowErrorMessage(STR_ERROR_PNGMAP, STR_ERROR_PNGMAP_MISC, WL_ERROR);
+		_switch_mode_errorstr = STR_ERROR_PNGMAP;
+		_switch_mode_detailed_errorstr = STR_ERROR_PNGMAP_MISC;
 		fclose(fp);
 		png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
 		return false;
@@ -230,14 +235,16 @@
 
 	f = FioFOpenFile(filename, "rb", HEIGHTMAP_DIR);
 	if (f == NULL) {
-		ShowErrorMessage(STR_ERROR_BMPMAP, STR_ERROR_PNGMAP_FILE_NOT_FOUND, WL_ERROR);
+		_switch_mode_errorstr = STR_ERROR_BMPMAP;
+		_switch_mode_detailed_errorstr = STR_ERROR_PNGMAP_FILE_NOT_FOUND;
 		return false;
 	}
 
 	BmpInitializeBuffer(&buffer, f);
 
 	if (!BmpReadHeader(&buffer, &info, &data)) {
-		ShowErrorMessage(STR_ERROR_BMPMAP, STR_ERROR_BMPMAP_IMAGE_TYPE, WL_ERROR);
+		_switch_mode_errorstr = STR_ERROR_BMPMAP;
+		_switch_mode_detailed_errorstr = STR_ERROR_BMPMAP_IMAGE_TYPE;
 		fclose(f);
 		BmpDestroyData(&data);
 		return false;
@@ -245,7 +252,8 @@
 
 	if (map != NULL) {
 		if (!BmpReadBitmap(&buffer, &info, &data)) {
-			ShowErrorMessage(STR_ERROR_BMPMAP, STR_ERROR_BMPMAP_IMAGE_TYPE, WL_ERROR);
+			_switch_mode_errorstr = STR_ERROR_BMPMAP;
+			_switch_mode_detailed_errorstr = STR_ERROR_BMPMAP_IMAGE_TYPE;
 			fclose(f);
 			BmpDestroyData(&data);
 			return false;
@@ -447,15 +455,16 @@
  *  to a landscape representing the heightmap.
  * It converts pixels to height. The brighter, the higher.
  * @param filename of the heighmap file to be imported
+ * @return Whether the heightmap was successfully loaded or not
  */
-void LoadHeightmap(char *filename)
+bool LoadHeightmap(char *filename)
 {
 	uint x, y;
 	byte *map = NULL;
 
 	if (!ReadHeightMap(filename, &x, &y, &map)) {
 		free(map);
-		return;
+		return false;
 	}
 
 	GrayscaleToMapHeights(x, y, map);
@@ -463,6 +472,8 @@
 
 	FixSlopes();
 	MarkWholeScreenDirty();
+
+	return true;
 }
 
 /**
Index: src/heightmap.h
===================================================================
--- src/heightmap.h	(revision 22846)
+++ src/heightmap.h	(working copy)
@@ -22,7 +22,7 @@
 };
 
 bool GetHeightmapDimensions(char *filename, uint *x, uint *y);
-void LoadHeightmap(char *filename);
+bool LoadHeightmap(char *filename);
 void FlatEmptyWorld(byte tile_height);
 void FixSlopes();
 
Index: src/landscape.cpp
===================================================================
--- src/landscape.cpp	(revision 22846)
+++ src/landscape.cpp	(working copy)
@@ -1194,7 +1194,12 @@
 	}
 }
 
-void GenerateLandscape(byte mode)
+/**
+ * Generate the landscape, using the given mode parameter and current game settings.
+ * @param mode The GenWorldMode to use (GWM_EMPTY is not handled)
+ * @return Whether the landscape was successfully generated or not
+ */
+bool GenerateLandscape(byte mode)
 {
 	/** Number of steps of landscape generation */
 	enum GenLandscapeSteps {
@@ -1208,7 +1213,7 @@
 
 	if (mode == GWM_HEIGHTMAP) {
 		SetGeneratingWorldProgress(GWP_LANDSCAPE, steps + GLS_HEIGHTMAP);
-		LoadHeightmap(_file_to_saveload.name);
+		if (!LoadHeightmap(_file_to_saveload.name)) return false;
 		IncreaseGeneratingWorldProgress(GWP_LANDSCAPE);
 	} else if (_settings_game.game_creation.land_generator == LG_TERRAGENESIS) {
 		SetGeneratingWorldProgress(GWP_LANDSCAPE, steps + GLS_TERRAGENESIS);
@@ -1277,6 +1282,8 @@
 	if (_settings_game.game_creation.landscape == LT_TROPIC) CreateDesertOrRainForest();
 
 	CreateRivers();
+	
+	return true;
 }
 
 void OnTick_Town();
Index: src/landscape.h
===================================================================
--- src/landscape.h	(revision 22846)
+++ src/landscape.h	(working copy)
@@ -93,6 +93,6 @@
 void RunTileLoop();
 
 void InitializeLandscape();
-void GenerateLandscape(byte mode);
+bool GenerateLandscape(byte mode);
 
 #endif /* LANDSCAPE_H */
Index: src/openttd.cpp
===================================================================
--- src/openttd.cpp	(revision 22846)
+++ src/openttd.cpp	(working copy)
@@ -71,7 +71,7 @@
 #include "table/strings.h"
 
 /** Error message to show when switching modes. */
-StringID _switch_mode_errorstr;
+StringID _switch_mode_errorstr, _switch_mode_detailed_errorstr;
 
 void CallLandscapeTick();
 void IncreaseDate();
@@ -459,7 +459,7 @@
 
 	_game_mode = GM_MENU;
 	_switch_mode = SM_MENU;
-	_switch_mode_errorstr = INVALID_STRING_ID;
+	_switch_mode_errorstr = _switch_mode_detailed_errorstr = INVALID_STRING_ID;
 	_config_file = NULL;
 
 	GetOptData mgo(argc - 1, argv + 1, _options);
@@ -1008,8 +1008,8 @@
 	}
 
 	if (_switch_mode_errorstr != INVALID_STRING_ID) {
-		ShowErrorMessage(_switch_mode_errorstr, INVALID_STRING_ID, WL_CRITICAL);
-		_switch_mode_errorstr = INVALID_STRING_ID;
+		ShowErrorMessage(_switch_mode_errorstr, _switch_mode_detailed_errorstr, WL_CRITICAL);
+		_switch_mode_errorstr = _switch_mode_detailed_errorstr = INVALID_STRING_ID;
 	}
 }