Just an update from me as well, last night I was having the problem, then put my PC to sleep for the night, and woke up this morning and Poser 8 is working fine.  No reboots inbetween and no changes done to Windows inbetween.
Now isnt that just the strangest thing?

I didnt even have to reboot in Diagnostic mode either.

The only thing different between now and last night was that last night, Windows Update was downloading updates in the background.  Right now, it isnt, and I cannot say for sure whether or not it was running in the past when this Poser problem was happening.

(Man, computers are just soooooooo strange, Ha ha ha)
I dont want to rule this out as FIXED though, because the day before yesterday, everything seemed to work fine, while the day before that, it was "broken" again.