I just made a set of replacements for the first (named "heart") CAS face, using AllenABQ's base templates. To my knowledge, I've followed the instructions (here) perfectly, even did the whole process slower than usual to make sure, and I've made a few perfectly funtioning replacement faces already.

I can load up BodyShop fine, and use makeup, hair, eyes, etc... But when I try to click on a premade face, or face part such as forehead/eyes/lips, the game just freezes and won't respond. Can anybody hazzard a guess as to what I've done wrong?

Out-of-the-stomach, I would guess you accidently use an older BS version. When installing a new EP / SP, the install routine will update the links to the new game's executable and will also update BodyShop, but the latter is not linked to by selectable program icons. I always have to do this manually.

I also use AllenABQ's templates (among others), and I only noticed a slight performance decrease when it comes to selecting facial details like beards, make-up, jewels etc. But no crash.

You know, I think you could be right there. I'll have to redo the set and make sure I'm using OFB BodyShop (my last installed/most recent EP). Thanks a bunch if it does work.