in this forum quite often problems are posted which originat from corrupted world.x0 files in the "savegames" folder.
I just realised how this can happen. My Windows XP broke down and when I restarted BD I got the error screen "BD was shut down incorrectly, do you wish to restore" (or similar, as I got this message in German). I agreed to restore old data and when I loaded the last stored savegame, my heroes were moving in an empty space, no walls, no trees, no items. This is typical for an destroyed world.x0 file. Fortunaltelly I had saved ten minutes before, too, and could continue playing with this earlier savegame, where the world.x0 was ok.
But if you just had killed some undestroyable monsters, it could be wise to exchange the corrupt world.x0 against a proper previous one. This is explained in detail in other posts (e.g. my post "cannot take key in lich cave").
Obviously, a Windows crash can cause corrupted world.x0 files in savegames that have been saved imediatelly before the crash. (I saved, then shut down BD, and during the shut down Windows crashed).