I resolved the problem with a new video card. Though all your suggestions do work when nothing else will, I found my previous AMD Sapphire 6950 (or it's drivers) being at the root cause of the problem. I replaced it with an MSI GTX 560 Ti 2GB Twin frozr II card and haven't had that problem since.. and it eliminated a lot of my other screen issues as well.. better card or better drivers? All I know is that the new card is soooo much better with Poser 2012.. and less expensive that the previous card..

Thanks to all who offered great advice.