Well, I made that one additional change in the display settings, upgraded to 4.09d (I goofed in my previous statement - I was on 4.08, not 4.06), and downloaded a newer video driver from NVIDIA. I've played about a half dozen songs so far without any video problems. I think it's too early in the game to swear that the issue is resolved, but one can hope.
Since it seems to mostly be a problem shortly after startup, I have to trying it multiple times of the course of the next few days and see if things consistently continue to keep working. I'll post back to let everyone know. Thanks to all of you for your help - much appreciated! (That's why we love MTU's forums!)