Actually, I had the same problem until I switched monitors. I was using an old Apple Cinema Display (circa 2004). I'm not using a generic monitor from Best Buy and I haven't seen the problem anymore. I also switched my mini displayport to DVI adapter to a Monoprice one for $6.65. So it could be either one that fixed the problem.
All I know is before Mountain Lion, I never had the issue using the old adapter and Apple Cinema Display. It's a shame. Considering it's an Apple monitor, it should just work.I believe it's a model A1081.
I have had this problem on all version of Lion, and now experience a version of it on Mountain Lion 10.8.2
Whereas I used to see transient display corruption artefacts, the new failure mode is an unrecoverable display corruption where the display fails to update and the console log fills up with NVDA(OpenGL): Channel exception! exception type = 0xd = GR: SW Notify Error messages.
This error requires a hard power-down to recover.
There are other threads that describe the NVDA channel exception errors on these forums, particularly with ML.
I would first try the Combo updater: http://support.apple.com/kb/DL1581
Then, try restarting using the Recovery mode (hold R at startup) but obviously not reinstall OSX (althought you can try that without losing your data). One you're in, go to Utilities up top and run Disk Utility. Check or Repair disk, and repair permissions. Restart.
Then try resetting the PRAM
or maybe if you have the nvidia card, you can udpate the driver. That seems to be the solution for many, depending on what model they have. What year/model is you Mac?
You can also try booting up with only one stick of RAM in (if you have two) and no other devices connected, just power. If nothing happens, try using the other RAM stick and take out the one that's in there. Also try switching the one that's in to the other slot. Could be that the RAM went bad.
There's also Apple's built-in hardware test. http://support.apple.com/kb/HT1509
Make sure you do the full scan. It could take a while, but it'll scan everything, including your RAM for failures.
If nothing else, schedule an appointment at the Genius Bar, and they'll check it out even if it's no longer under warranty. It could be defective or a recall issue and you might get it fixed quickly!
In the end, after a year of hoping the the next OS X update will fix it, and trying all the usual remedies (safeboot, repair permissions, SMC reset, PRAM reset, avoiding Flash content, changing my browser) nothing was working in ML 10.8.2 to prevent NVDA channel exception graphics crashes. I decided it was high time to let Apple have a go, even if it cost me. The Genius Bar was able to reproduce the fault and they sent it for a depot repair where they changed the logic board and replaced my installed 3rd party (Crucial) 8GB of RAM back to 4GB of their own preferred RAM.
The final result is a fully working Macbook Pro with no graphics issues whatsoever.
I am left with the question as to whether the RAM was really implicated in the problem, or whether they changed it out just for safety.
Nevertheless, it is really nice to have a fully reliable Macbook back in my hands.
It would be interesting to know if any other posters here, after two years, are still struggling with the graphics.
Although I have an iMac (late 2007) with ATI rather than NVidea electronics, I have also been getting annoying transient graphics glitches since I upgraded from Snow Leopard skipping Lion, straight to Mountain Lion.
I have had the motherboard replaced but it has made no difference. I have Mavericks on a partition as a trial. Still the sproadic graphics artifacts.
It must be a software issue but where to look?