Hi thanks for the reply, this is what I have been stressing to explain. I have never ever got these kernel panics before its only since I updated to 10.8.4 about 4-5 days ago its happened twice. It's cant be just a coincident that it happens after I update to 10.8.4 and before that I have never experienced any problems.
It's not just me if you ask other people who are experiencing this they will also say its since they updated their machine to 10.8.4 it's been happening
Hence why I'm near enough 100% sure it's not the GPU, and it's got something to do with the update.
I have never ever got these kernel panics before its only since I updated to 10.8.4 about 4-5 days ago its happened twice. It's cant be just a coincident that it happens after I update to 10.8.4 and before that I have never experienced any problems.
The 10.8.4 update just likley exposed your already existing hardware issue, there isn't a whole lot of people here with issues with 10.8.4 and it is tested before release.
Printout or copy the panic report to a USB thumb drive.
Do what Kappy says, copy your user file folders to a external drive, use the zero erase and install OS X.
Take the machine into Apple for a free hardware evaluation.
They might be extending special cirumstances as they have been known to do so in the past, there might be no problems what so ever or they may want to charge you for a repair, it's their call.
If you decide not to pay to repair, then take the machine home and use it for some time without any third party software, then install one third party program at a time in a slow fashion as to see what can cause the issue and if you can live with it or not.
There might not be any more issues at all and despite having the GPU fault the machine could work just fine.
first I tried repairing disk permissions. seemed to help, for maybe a few days. then back again, and then auto restarted several times over just a few hours...
found somewhere suggestion to reboot into SAFE mode. then once it "fixed itself" in SAFE mode, reboot in regular mode. That was over a week ago and I have not had one auto-restart since. Yeah!!
well that was shortlived. I had one or two days without restarts, then it started again... frustrating. Finally just turned off computer. [Mac Pro 2008. 3,1 os 10.8.
Now back from trip. turned it on, same, several restarts per day. Cursor trapped upper left corner 6 minutes after each restart.
So I just re-installed OS X Mountain Lion.... we'll see what happens.
1st positive... cursor did NOT stick in corner after this first reboot.