I tried "last_error" already, but the engine crashes once it reaches the wait(1), so the last_error block is never reached.

Removing entities from the level one by one doesn't help as the crsah disappears once I remove or add an entity from the level. But I'm sure this is no fix at all as the error will just appear at another point of the game (if it is some memory issue).

mmm that sounds like completely bizzare behaviour, i thought it might have been a shared material or texture or script between them ,but adding a random entity to it takes away your crash , makes no sense to me , except what sounds logical is a memmory related problem as you mention , or an engine bug , have you tried out asking the dev's .

i mean what would adding/removing a random entity effect in the level itself before loading , all i can think about internally ,during loading ,would be the entity list , memmory ,pointers , shedule list , materials , textures , bounds ,hulls , stack sizes perhaps , the list could go on but only the devs would know what is internally effected.

I just asked JCL for help on this ... maybe I can get some more information about what really happens inside the engine with the first wait(1) after a level_load.

Lol, 8 pages now

Are you sure this isn't just a one time compilation problem? I mean, once you add or remove an ent, you compile again...and the crash disappears.
Try recompiling without touching it, and see if the crash still occurs.

Only recompiling doesn't help.

But changing the order of the entities inside WED helps. If I just delete a model, click undo and then recompile, the crash is gone. By deleting and undo the deleted model is set to the end of the list in WED and that helps. Of course deleting the last model in the list doesn't help as the order wouldn't change.

I can't fully remember, but I think there was a limit to 22 characters for action names or the like.
The mean part is: actually it's 21 characters (guess the \0 string end marker counts) and I know I had problems due to that that I was trying to go with an action name exactly 22 chars long
Can't remember whether the engine crashed or the function just was not started, though.

The crash is based on an engine bug:

http://www.opserver.de/ubb7/ubbthreads.php?ubb=showflat&Number=457806#Post457806

So this topic can be closed as solved.