I think something is wrong with a fan in my system, as last week one of them was making a noticeable noise when at low RPMs, and now I haven't heard that fan crank on in a while. And in that time, I have had the system hard freeze multiple times while playing World of Warcraft (high load on CPU and GPU), and last night had the graphics begin to deteoriate in game indicating possible damage to the video memory. I was under the impression the system had thermal protections built in to prevent this type of damage.
Environment wise, the MacBook is sitting on an iCurve stand with plenty of ventilation both under and above it. It is not being run in lid closed mode, and did work fine for a month.
I'm making a full system backup to a firewire drive so I can boot it on my Mac Mini for now. I just hope that Apple turns this around pretty quickly. The texture issues last night in the game have me really worried permanent damage has occurred to the system, as my experience with PC video cards doing similar is usually a downhill slope to the complete failure of the card.