Good call araneldon. I find some of those sysinternals utilities rather scary, but it did the trick. It's a pity in a way, because I was quite enjoying the wild speculation. :)

It was nothing to do with my registry cleaning. My network at work recently introduced a redirect for roaming profiles, and Poser was going directly to the remote server copy. Some applications seem to write to C:Documents and Settings and wait to be synchronised at log-on/off, and it seems that some don't.

I don't need to understand it, just be aware of it. I can relax now. :)