My laptop currently seems to be f’ed in the a. It has been behaving a little flaky in the past week or so (perhaps since the latest OS and graphics update.) I would come back to my desk and notice the screensaver had locked up and the screen had a number of pixels with the wrong color, seemingly random colors, but probably tied to the color palette somehow. I would restart from that, only to have it not quite boot entirely on the first try. Either things would get far enough to log in and see Finder (but no menu bar, similar problems with the color palette, and the machine locked up) or it would get a kernel panic part-way through booting. Throughout this all, the machine would get unusually hot. I’m used to the machine getting hot–between recompressing video and recompiling code, it can get toasty–but I’m talking REALLY unusually hot. After letting the machine sit for a while (to cool off?), it would boot fine. While running, I didn’t notice anything unusual with the temperature sensors or the fan RPMs.
Last night, I did some poking around to see if I could fix things. My AppleCare disc doesn’t seem to want to boot, but I could boot from the Leopard install disc. Disc utility reported nothing of interest (a few permissions problems that were fixed.) Dropping to a terminal to look at syslog showed all kinds of graphics-related error messages before/during/after the panics, but I’m unsure of the causal relationships (did the graphics hardware cause the kernel to crash, or did the kernel crashing affect the graphics drivers?) After rebooting back to the OS, everything seemed fine. In fact, I was even able to do some heavy graphics work on a flyer for Kim.
Today, I had another crash and thought I would spend some more time trying to fix things. I reset the NVRAM/PRAM and the SMC, which seems to be the first thing to do when experiencing something odd under OS X. After that, I could boot up to a locked Finder with no menu bar (as above), and rebooting causes a kernel panic part-way though bootup (a few seconds after hitting the gray Apple screen with the spinny wait cursor.) And now, no matter how long I let it sit and cool down, I get the same kernel panic partway through boot. Trying to boot to single-user mode (by holding down the shift key) seemingly crashes in the same place, but just takes longer to get there. The whole while, the machine gets unreasonably hot.
I’m hoping this is something that can be solved by reinstalling the OS tonight, but fear that a part on the motherboard may now be thermally fried necessitating a trip to the Apple Store tomorrow. Fortunately, because I have Apple Care, it won’t cost anything but the annoyance of not having a laptop for days/weeks.
My PBG4 has simmilar symptoms. sorry to say it required a mainboard replacement.