After all my problems with the OS X 10.5.7 update the next step was to run hardware diagnostics. No sense doing a third fresh install unless I knew it wasn’t a hardware problem unearthed by the upgrade.
Unknown to me, until I started checking was that every Mac comes with hardware diagnostics on the bundled DVD. This Apple support article describes which DVD the hardware diagnostics are on and how to run them. I’d also recommend you disconnect an non-Apple peripherals including hard drives, which I did.
Some things to keep in mind. Hardware diagnostics is only on the DVDs bundled with Macs, it’s not on any upgrade DVDs you may have bought. In reading the Apple support article keep in mind it refers to the version on original OS X DVDs when looking for the right DVD. In my case it was DVD one and there was also a hardware diagnostics readme on the same DVD. This readme warns that test times may be longer than estimated if you have more than 512MB of RAM. In my case the regular test was estimated at 1 to 3 minutes and took only 1 1/2 minutes on my white iMac with 3GB.
I also ran the extended test which was estimated at 5 to 10 minutes and took 12 minutes. Interestingly, during the extended test the progress bar never went past the half way mark, but it did say no problems were found and the test completed successfully.
If you purchased Apple Care for any Mac you received a copy of TechTool Deluxe. You can download an updated copy from Apple’s Support Website. You’ll have to enter the serial number of your covered Mac to get the update. Instructions for using TTD are available in the Apple Care welcome kit or on the download page after entering your serial number. TechTool Deluxe is also sold as a separate product which I believe is slightly different than the one bundled with AppleCare. I used the AppleCare version of the product.
To use TechTools Deluxe you can either create a bootable DVD or install it to the hard drive. I installed it (to the applications folder) and ran it from there. Like Apple’s hardware diagnostics no problems were found.
None of these hardware diagnostics found any problems with my hardware, so I guess it’s on to yet another fresh install. But I’ll save that for another night. I know the problem hasn’t gone away as my iMac locked up again last night while watching a video but further troubleshooting will have to wait.