I wonder if Vista is part of the problem. I used to run XP-64 with Poser 7, but due to driver problems with the new hardware, I had to switch to Vista-64 and went ahead and upgraded to Poser Pro at the same time. I've gone through the trouble of disabling all of the unnecessary Vista services:
http://www.vistax64.com/tutorials/81176-speed-up-performance-vista.html

Time to try OS-7 huh? I've heard it runs much better than Vista.

My video card is an nVidia GTS 8800. An ATI video driver might help solve the problem with an ATI card, but I find it curious that I'd have the same issue with an nVidia card. So, chances are this is more than a video card issue.

And for what it's worth, the 64-bit machine running Poser only has Poser, Adobe PhotoShop and Carrara. It is only for doing art. No MS Office, or other non-essential programs. 

Everyone's comtribution is wonderful, I'm just trying to help narrow the field of possibilities.

-p