Well, guess what.  Problem solved.  And the problem was me.

The other night, I visited Pixologic.com and learned about their ZBrush program. While watching a few of their tutorials, I noticed the same jerky motion in their program that I had experienced in Poser 8. I have no idea what specs they were running, but I finally understand that, with 3D apps, you can have a top-of-the-line setup and still have it slow to a crawl depending on the program you're using and how many poly's you're working with. I was just too accustomed to having D|S run flawlessly with any camera, and couldn't grasp why Poser can't deliver equally smooth motion regardless of which camera I look through. I'm guessing that D|S's modular design allows it to create a smaller footprint when loading into RAM.

Anyway, after that revelation, I surfed around to other 3D sites and found myself itching to try Poser again. There's just so much more content and community support for it. After looking up this thread, I realized I hadn't yet tried Poser again since upgrading to Windows 7. So, I crossed my fingers and re-installed Poser 7. I'm very happy to report that, while the jerky motion is still present when using the Face and Hand cams, it's not nearly as pronounced as it was under XP. Unfortunately, 3DConnexion still hasn't released a driver for my Space Navigator to work with Poser 8, but I'm too excited about getting back to modeling to care at this point. Besides, it works beautifully with Poser 7.

I'll be re-purchasing my Poser 8 upgrade license in a few weeks. Meanwhile, it's time to get back to learning Poser 7.

:D

BTW - I still have the invoice I got from Content Paradise, with active links to Poser 8's installer and content. Is re-buying the license simply a matter of re-ordering the upgrade?