G5 display problems solved

I've been having some trouble with my G5 over the last couple of months. Intermittently, it wouldn't boot up, though the power LED would light, and the drives seemed to spin up to speed.

At first, I thought it was an immediate kernel panic, possibly resulting from my keyboard or mouse drivers, partly because it didn't appear that holding down "shift" for safe boot or "C" to boot from the optical drive had any effect. At first, it seemed like it would boot every 2nd time I tried, but as weeks went by, it seemed to be less likely. Fortunately, the machine is very reliable, and didn't need to be rebooted, except for System Updates. Unfortunately, there have been a lot of system updates lately.

I discovered that if I opened up the case, reset the Power Manager, and put everything back together, the machine would boot cleanly. I did a little more web research, and discovered this link from the Mac Owners Support Group, which led eventually to this Apple support database entry. It turns out that there's a known issue with certain ATI video cards, which show up in System Profiler as Card Model "ATY, RV350." Mine is an RV360, but other sufferers reported a fix just from removing and reseating their video card.

That fixed it for me, as well, and pointed up the worst part of the otherwise brilliant G5 case design: The screws that hold cards in place are hard to get a screwdriver on, because they're (a couple of inches) behind a lip. If you've got an offset screwdriver, this is the place for it.

UPDATE 5/24/07: This didn't actually fix things. Somehow, I got two consecutive reboots without a failure, but not three. When the new Security Update came out today, I installed it, then shut down the machine, reset the PMU, unplugged the power cord and all the cables, and rebooted. The machine came up, worked on installing the updates for a while, then rebooted again. D'oh! Since then, I've been unable to get the machine to come up at all, and somehow, I've made things worse -- now the machine only flashes the LED for a half-second when I try to reboot. More as it happens.