Hey...
It sounds to me like this is could be a cooling problem and NOT a faulty GPU issue.
No GPU remains stable if it is overheated. The fact that these machines aren't cooling properly sounds like a fan/cooling/SMC issue.
Has anyone been able to recreate the artifact symptoms under "low temperatures?"
I just got my brand new 17" MBP last night. I ran two 1080p HD movies simultaneously at full screen. The CPU/GPU heated up to about 80 degrees celcius and the fans increased from 2000 rpm (standard) to 3500 rpm. It dropped the temp back down to 70 degrees and held it there. I saw no artifacts.
However, tonight, I'm going to try the same experiment, then put the computer to sleep ( *there is a reported problem that the SMC "forgets" the proper fan speed settings after waking from sleep* ) and then I'll try the experiment again. If the fans don't speed up and artifacts are visible, I'll deduce this is a cooling issue and not a GPU issue.
Luckily, Apple can just release an SMC Firmware update to fix this (if my theory is accurate). In the mean time, we can use a 3rd party app like SMCFanControl or FanControl.
REQUEST: To Everyone who is experiencing this problem... install the FREE app "+iStat Menus+" to monitor your temperature and fan speeds (
http://www.islayer.com/apps/istatmenus/). Resume your heavy lifting using the NVIDIA 9600 and note if your fan speeds increase when the CPU/GPU heats up. Post back with the following info:
1) GPU Temperature at which artifacts are first visible.
2) Fan Speed (RPM) when artifacts are first visible.
2) Did your fans speed up when the GPU got hotter? YES/NO What temperature?
(Make sure you are reporting the GPU temps, not the CPU.)
This data should help us determine the true cause of the problem.