Q: NVDA(OpenGL): Channel exception!

Thanks so much for letting us know. I filed a bug report again saying that the graphics update didn't fix the problem. I wish I had noticed this while it was still under AppleCare. It's not really fair that the driver problems emerged while the machines were still under AppleCare, but Apple didn't fix the drivers.

I will avoid NVidia cards as much as possible from now on.

After bragging to my wife about the reliability of Mac Hardware & Software, I convinced her to replace her Windows box for a Mac Mini. The new line had just come out with the new "next generation" NVIDIA GeForce 320M graphics hardware..... You guessed it. It's been working well for a couple months. Last night I shut it down to protect it from potential lightning surge. Thought to myself at the time, "this thing runs really warm, hope thermal shock doesn't take it out". My wife plugs it in and powers it up this morning, starts Safari, starts Itunes..... LOCK. Similar symptoms as this thread describes. Pointer moves, the rest of the graphics are frozen. I logged in remotely, & the system appeared to be fine. Attempts to reboot remotely failed, however, 'sudo shutdown -n now' worked.

I rebooted it several times, each time it would lock up moments after starting the browser or Itunes. I booted once more, but avoided those apps. Finder, diskutility, console, worked fine. I noticed the error - NVDA(OpenGL): Channel exception! I continued to avoid the apps that caused the lockup and left the system up for over an hour, then went back and played with other apps. Still working! Then I started Safari - BANG!

Being a novice at MAC administration - I went to the diskutility and ran the permissions check utility - a zillion lines spewing "incorrect permissions" mostly related to airport - something I've never messed with. I ran the "correct file permissions" & rebooted, ran "correct file permissions" again and rebooted again.

The system has been running well for several hours now.... Am I lucky? Will continue to watch.....

just to check, have you run software update and applied the graphics fix from it?

I don't recall applying the Graphics update..... but apparently I must have, when I check for updates, there are none pending.....

FWIW, shutting down isn't enough to fully protect any computer or associated equipment against lightning surges. You really need to unplug it from everything that might send high voltage surges through it, including any cables attached to other equipment with the same risk. I just lost a cable modem to a strong surge from a lightning strike that didn't even hit anything nearby.

Also make sure you shut it down properly before killing power to it. Failure to do so can corrupt files that haven't been completely written out to the HD yet or to directories that haven't been updated. For the same reason, it is also a good idea to run Disk Utility's verify disk step after any time power has failed.

I have switched browsers a week ago. I started using Chrome because I was getting way too many beach ball pauses with Safari.

While they haven't gone, it - unscientifically, I admit - seems to have become less. There are still pauses, with the usual garbage in Console, but not a frequent.

Might be a way to ride out this 1,5 year long storm. Apple is sitting on its hands.

safari and chrome are gpu accelerated i believe, how's firefox?

Last night I finally updated from 10.6.2 to 10.6.4 and experienced the display issues well described in this thread (I have a 2.2Ghz mid-1997 SR MBP, GeForce 8600M GT graphics). Lots of these in my kernel.log:
NVDA(OpenGL): Channel exception! exception type = 0xd = GR: SW Notify Error
System was unusable, with all sorts of display artefacts and regular freezing (mouse cursor would move but otherwise the system would freeze for a few seconds, this occurring several times a minute).

Installing the post-10.6.4 graphics update didn't help, so, clutching at straws I ran DiskUtility and did a "repair permissions". As with snowclone's experience, nothing graphics-related seemed to be repaired, just a lot of things relating to Airport. Rebooted and my machine has been fine for ~12 hours now - no problems and no more video-related errors in the logs.

Thanks to snowclone for the suggestion!

I also own a white 24" 2.16GHz iMac, which 8 month ago has started to produce the NVDS OpenGL Channel Exception error messages and the screen gets buggy, even the OS frozen. Tried everything, but not yet the VGA board replacement since it would cost half of the price buying another used one. Dismounted and blowed with air duster, etc, nothing helped but was thinking about what it VGA card overheats because under lower load the problem not always materialized.

*Got the idea:* is there a FAN control application available? Found the FREE Fan Control application (http://www.lobotomo.com/products/FanControl) which is a pane in system preferences and shown that CPU Fan (which cools the VGA too!) rotates only 1200rpm. Guess what! I have set it to rotate at a minimum of 2500rpm and since then the logs are clear, no freezing, no buggy screen, etc, even after editing the 100th RAW picture in Aperture 3 (which was my OSX killer app prior...)

I am testing this method since 2 days, leaving lots of full-flash web pages open for all night and *the system is stable*.

I am happy now (I have used thic computer for a year prior the error ruined my iMac usage), give it a try if really overheating was the cause of the error...

If the "NVDA(OpenGL): Channel exception" problem is thermal related, then most posting on this thread would occur during warmer summer months of the northern hemisphere where most people live. I tallied the postings by month from the beginning of this thread in (Feb 22, 2009) until the latest:

Count Month
2 01
7 02
4 03
6 04
23 05
38 06
23 07
66 08
46 09
16 10
2 11
1 12

Running my tally script on other support threads that are over a year old does not show such an amazing seasonal correlation.

It is a thermal problem and not caused by a particular OSX release.

I think I am inclined to agree with your assesment. In my previous post, I mentioned I ran fix permissions in the disk utility, and my problem (which was consistently happening within a few minutes after rebooting), disappeared for nearly a day, then came back sporadically for the next 24 hours (2-3 times), then today I was back where I started, with no more than a few minutes after booting before the big freeze. I came back to this thread to post my failure and saw LordBBK's post. I did think my Mac Mini (3 months old) was running pretty warm, but dismissed the thermal failure theory because the symptoms did not seem to fit. I mean I was getting constant failures, I run disk utility, reboot and they go away - immediately! I did not turn off the power and let it cool for any amount of time!

Regardless, since we all know that hardware failures can be much more elusive than software bugs, I thought I would give his suggestion a try. I rebooted in safe mode and installed the fan control program. I figured that since safe mode disables some of the more advanced graphics functionality, maybe I could get the controller installed before the box froze again. It probably took me more than 20-30 minutes to do, as I didn't realize that Safari wouldn't work in safe mode (it just clocked), so I ftp'd the package from my other Mac that I had downloaded the package to.

My initial fan speed - I think was 1800 RPM. I bumped it to 2300 & rebooted into normal mode. It's been up 4 hours now.... I not ready to say we've found the root cause here, because I've been here before, but I post an update tomorrow and let you know how it goes! Fortunately, I still have 9 months of warrenty left!

Many thanks to LordBBK & Mr Pi ! I am beginning to feel hopeful !!

Update 1: Its been more than 18 hours - no freeze yet!

22 hours - it froze again! I pushed fan to max (~3600RPM) Temp ~107 degrees. Clicked Applications on the dock, window opens, screen freezes... If this is thermal, it's happening at very low temps!!

it's the nvidia drivers. fyi- best keep an eye on your hd temp if you're manually adjusting the fan, if it drops towards 30 you're endangering it's longevity (the lubricants are less efficient at lower temps)

Personally, I don't think it's completely thermal related. I'm on a 2006 Mac Pro and occasionally get the errors, and my temps and airflow are always good. I control them with SMCFanControl.

-Kevin