I've got an Intel Core Duo iMac running OS 10.4.11 which freezes on me sometimes. The only solution is to turn the machine off. It seems to happen randomly--not while in any particular application. The machine came with two 512mb sticks of RAM. I took the machine to the Apple service agent, but it did not freeze while he had it. He suggested new RAM, so I bought a single 1GB stick of RAM to replace the two 512mb sticks. With only the new 1GB stick installed, the problem persisted. I called in another tech over to my house who ran DiskWarrior which found no problems, and the tech could not determine the source of the problem, but thought that there might be a conflict in a software update or something. We did a reinstall of the system, but still the problems happens. In addition to the freezes, it sometimes goes black like it's gone to sleep, but doesn't wake up and has to be restarted. On a couple of recent occasions while booting up, after the sprocket, it goes to the blue screen and freezes at the blue screen. Any suggestions? Does this sound like a hardware or software problem? Would upgrading to Leopard be a solution, or could that compound the problem?
Thanks ahead for your input!