It seems that after you kill a "white square entity" (white square in the entities list, created by players), the game becomes unstable and will randomly crash after that. That could also explain some crashes players had.
You can also try this : kill the entity, and press F2 in edit mode to save, the game will crash.
If you update the entities.txt file in the Aquaria directory (scripts/entities/entities.txt) to declare an id and graphic for the entity, the problem is solved.
The only thing is I don't like modifying the game's files when installing a mod, but I guess I won't have the choice.
