I've seen this in 7 with sr1 and sr2. Namely hair wigs (or anything that is a prop attached to the head) see to get their geometry shifted around and not from poses. Its as though the actual origin of the hair gets moved so that a position of 0,0,0 becomes some other numbers but the wig stays still. Then, after some moving it will shift around. I have double checked to make sure this isn't just some pose that effects hair. For example I also have masks on characters and earings and they move around too. I also made sure they are children of the head and not of some clothing head.

I think it is something to do with the preview settings under Preferences.  You need to play with the OpenGL hardware enable preview rendering, etc etc.   Or use the software renderer.

Eternal Hobbyist