It was Bot_Blockoshooter
Sounds to me like that is trying to change what slot images are mounted to, which is garenteed to cause a stuffton of incompatibility.
Sorry for not working on hatmod at all, I've been busy with my RPG, and haven't been in the mood to work on it. It needs a serious rewrite now that I've learnt a bunch more (OO stuff mostly, no more using global arrays to store hats..)