Well I've just realised that my new player model has 2 additional no texture skins (with UV mapping) again which the old one didn't. I'm pretty sure the error only appeared on/ with models which have skins with no textures.

Can you please double and triple check that part in the engine again?
(Btw. the error happens between "LevelReady" and "def_startup started" but I assume you are aware of that.)

EDIT: The mini example from some time ago still crashes on my machine. Is there something I can do with it (except strapping it down a little more) that helps you in finding the cause of the error (including stuff you may send me which I test)?


EDIT2: Made the old example even smaller: http://superku.de/mdl_crashNew.zip
The error does not appear regularly, sometimes on the first try, sometimes it doesn't appear 7-8 starts in a row (with this linked example). - Crashes without the view entity too:

Code:

///////////////////////////////
#include <acknex.h>
#include <default.c>
///////////////////////////////

void main()
{
	fps_max = 60;
	video_mode = 9;
	level_load("test.wmb");
	wait(4);
	ent_create("tile3.mdl",vector(128,0,32),NULL);
	vec_set(sky_color,COLOR_BLACK);
}

And even smaller: http://superku.de/mdl_crashNew2.zip
Now it's only a few lines of code, a NULL level and one entity ("tile3.mdl"). If you remove the empty skin(s) (or load "tile3b.mdl") the crash is gone. Otherwise, after 5-6 starts at the latest the error should appear.