My Human Peasant with a removed Pick-Ax and Blademaster Animations works fine, but the following do not (And this sucks, since I spent like 8 hours on them):
Troll Headhunter (I fixed some bone names with this model... that might be it?) without spear or quiver with Demon Hunter Animations
Priest without Staff with Demon Hunter Animations
Grunt without Axe with Shaman Animations
They work fine in Magos' model viewer. Just they crash when I try to use them.
MDL editing is really, really specialized. A little, very little change can make the model crash, as Mecheon said. How to fix it? Try to compare the original mdl with you modify; misplace space can make the model crash (this is an exemple).