I'm having a weird problem that's kinda hard to describe It seems to be related to pasted backdrops and collisions but is unrelated to previous collision problems I've mentioned in other threads... Basically I have an Zelda 1 dungeon-like engine. When the character moves past the screen edge the next "room" is drawn and then the game scrolls. When the scrolling is done the previous room is removed.
It works great but when moving the character to the room above the starting room the game will crash. I can move to any other room on the map apart that one. The attached image shows what I mean. 'S' is the starting room, green arrows are passable doors and the red arrows show where the application will crash. It doesn't seem to be the actual scrolling that make it crash though, but the loop that add backdrops before the scrolling takes place. Disabling the backdrop pasting loops will make it work again.
You can see the lines that trigger the crash in this print screen. Changing those three lines to comments will stop it from crashing but probably breaks collision detection or something.
Any help is appreciated. I could make a stripped-down version of the application if needed. Thanks!