You don't say which version you are using. Poser 7 sometimes acts a little wanky after viewing FLASH files (in Internet Explorer at least). Minimize the program and hit your space bar and then go back into Poser.  Sometimes that fixes things.  I’m finding Poser 7 doesn’t like being left alone on the desktop for long periods of in-activity.  Again, minimize the program and maximizing again seems to fix the problem.

Does your problem occur with all conforming figures or is it a certain set?  Might be a problem with the actual figures … Might be too the pose file is corrupt or missing some information.

I suggest trying to minimize/maximize the program window BEFORE doing an undo.

Best Wishes,
Rªnce

PS: drinking a little Scotch tonight so you may wish to completely disregard my reply