Currently I'm trying to remove as much of the game code as possible to track the issue down.

I just noticed that at least WED doesn't seem to like long level names.

#define PRAGMA_LEVEL "upper_library_floor.wmp";

leads into an "invalid name" exception when loading a level in WED.
Does someone know if the engine has also a limit here? I just want to keep sure that the crash doesn't come from those long level names.