I've had a bug where the walls and background will disappear from a room, although placed objects remain. This seems to apply to a room, even if I leave that room and come back. For instance, I had it happen to the town map, so that I could only see the buildings on a green grass background.
Also, the game seems to sometimes set its resolution to 800x600 then immediately crash when I try to alt-tab out while it's in fullscreen mode.