G5 imac, ALS, new in May, 2005. Has gone through 2 powersupplies, the superdrive, the hard drive, and a midplane? assembly. The last couple of problems have been the powersupplies. Symptoms include sudden shutdowns that become more frequent until it refuses to start at all, just a second of glowing light on the power button, and darkness. Replacing the powersupply has fixed the problem the last two times. 2 days ago it started shutting down, again. No warning. CPU temp after the last one was in the 68 range, then dropped down to 53 after a bit of light use. Any suggestions? Replacing the powersupply again doesn't really seem to be a long term fix. I'm somewhat annoyed... (it is under Applecare, the powersupplies have been diagnosed and replaced by certified geniuses...) Running 10.4.8, all updates, 1.5gig ram, Seagate 320gb drive.