In frustration I made a backup of my laptop hard disk, and did an erase-and-install with Tiger from the install DVDs that came with the laptop. Mind you, the Apple Hardware diagnostic gives this machine a clean bill of health. With the original 512MB DIMM, with nothing plugged in but the power cord, and with a fresh Tiger install, even following an SMC reset, I can crash it. So, this is apparently not Leopard’s fault.
It does take about 45 minutes of heavy use to make it crash, though. I made an iDVD project and had that looping in preview mode, opened about a dozen partly transparent terminal windows running top -s 0 overlapping that, played a DVD behind all that, and ran the two .qtz movies in /System/Library/Screen Savers.
I also tried a bunch of intermediate stages of downgrading and testing, including 10.5.0, 10.5.1, 10.5.2 without the Leopard Graphics Update, then with it, 10.4.6 (from the DVD), 10.4.11 with all the current stuff, with and without external display, with and without a shim propping up the bottom of the case with a desk fan blowing directly at the underside of the case. No matter what, I can make it crash, but it takes a good half hour or more before it happens.
Plugging in the external display seems to help (it crashes much more quickly with the external display connected). My guess is that the GPU or VRAM is overheating or is just plain faulty, and that increasing the number of pixels they have to drive is what makes them fail faster.
I had suspected that it might be a GPU temperature problem, or even the dreaded Thermal Paste misapplication problem, but using iStat and Bresink’s Hardware Monitor, I wasn’t able to find a correlation between GPU temperature and a GUI crash. But, now that I can prove that it isn’t due to any non-Apple hardware, and that the OS version is irrelevant, this MBP is going back to Apple for repair. Again.
Again? Yes. I had a somewhat similar problem before, but the video artifacts were much more hardware-y in nature. Apple blamed it on 3rd party RAM and told me if I continued to use non-Apple RAM they would charge me for the next logic board, regardless of AppleCare coverage. So I’ve been using Apple RAM, which costs about twice as much as the Patriot RAM I had bought originally.
However, that problem was visible to the Apple Hardware Diagnostic software. This one is not – the diagnostics find nothing wrong (even on the extended diagnostics mode), but in real world usage I get about 2-4 hours of uptime before having to restart. Even, as I said before, under a fresh Tiger reinstall with Apple RAM, and nothing but the power cord plugged in.
Hopefully Apple service folks will be able to reproduce this problem, or diagnose it with some kind of fancier tool that runs for long enough to provoke a failure. I apologize to anyone who has followed in my diagnostic footsteps, which now appear to have been off track.
Update: It was actually an intermittent hardware problem and Apple has replaced the logic board of this computer.