Hi Ann, I'm wondering from this post, if possibly the Monitor or cable losing connection for an instant or such?
Might see this too...
One way to test is to Safe Boot from the HD, (holding Shift key down at bootup), run Disk Utility in Applications>Utilities, then highlight your drive, click on Repair Permissions, Test for problem in Safe Mode...
PS. Safe boot may stay on the gray radian for a long time, let it go, it's trying to repair the Hard Drive
Reboot, test again.
If it only does it in Regular Boot, then it could be some hardware problem like Video card, (Quartz is turned off in Safe Mode), or Airport, or some USB or Firewire device, or 3rd party add-on, Check System Preferences>Accounts (Users & Groups in later OSX versions)>Login Items window to see if it or something relevant is listed.
Check the System Preferences>Other Row, for 3rd party Pref Panes.
Also look in these if they exist, some are invisible...
Have you blown the dust out lately?
Get Temperature Monitor to see if it's heat related...
I've got a very similar issue. I've posted the topic here: http://apple.stackexchange.com/questions/93618/any-advice-on-troubleshooting-ins tability-in-mountain-lion-os-x-10-8-4
> NVDA(OpenGL): Channel exception! exception type = 0x1f = Fifo: MMU
> Error Jun 10 13:14:44 JustinMbp kernel: NVDA(OpenGL): Channel
In all cases of crashes, I can SSH to the machine, but I can't figure out anything useful to remedy the situation.
This freeze happened when sizing the crop in Aperture. Machine had been running for probably 3 days.
Apple support wants to me uninstall every system extension, etc. to troubleshoot. They can't seem to find anything in the logs. I find that hard to believe that this issue cannot be troubleshooted via ssh or the logs.
Needless to say, freezing every 3 days is awful. My guess is that the issue is related to updates related to Aperture or Chrome. I'm pretty sure I've been running Chrome every time the machine has crashed. I'm also sure the machine has sometimes crashed without Aperture running.
Any advice on how to troubleshoot?
Is there any way to have the dual video card only use the NVidia card rather than the Intel one (when using A/C)? Could that be relevant?