Intermittent System Hang at Restart and Shutdown

Question

Hi Everyone,
I finally got around to upgrading my old iMac G4 to Leopard yesterday, and almost immediately found a problem that's driving me nuts...
It started right after I installed Leopard from the DVD using Erase and Install, and updated to 10.5.7 using the combo updater. After the combo install completed successfully, I clicked "Restart," and was immediately left with a blank desktop (just the wallpaper, no icons, no menubar and no spinning pinwheel/spokes on the desktop as some others have seen) and the cursor (which is responsive). It looks like the Finder and Dock quit, and the restart or shutdown procedure then came to a halt. Some keyboard shortcuts still work, such as the ones to open the shut down dialog box, and the force quit box--but clicking any of the buttons does nothing. The keys for brightness, volume and eject also still work. The HD was quiet, and after about 5 mins I held in the power button to shut down. After restarting, I opened Console and found no log entries at the exact time I clicked Restart--in fact, nothing logged until the next power up.
I restarted and shut down a few times after that, some while using Software Update. About half of those times, the hang occurred, and if there were any other open apps, they did quit along with the Finder and Dock. I decided to reinstall 10.5, using Disk Utility on the DVD to write zeroes to the disk before reinstalling. From there, I applied the 10.5.7 combo update--and from there the problem started again, and still apparently without any log entries. It's worth mentioning that I tried Leopard on an external FW LaCie HD connected to this Mac a few months ago (ver. 10.5.4 then), and the problem existed then as it does now.
Other tidbits: The internal HD I'm using is less than a month old, and worked well with Tiger. The Mac passed the Apple Hardware Test on the original install CD. Disk Utility on the Leopard DVD found no problems and no permissions errors. I've used the Spotlight prefpane to stop it from indexing the HD, and I have Time Machine turned off. I've reset the PRAM. There are no peripherals attached other than the keyboard and mouse. There is no third party software installed (yet). I've tried looking at the forums on MacFixIt, and using google, but haven't found an answer. Any ideas?
Thanks for helping,
Eric

Answer 1

Update... After trying to find the source of the problem for a three weeks, including trying another Erase and Install using Kappy's suggestions, only to have the hang continue to occur repeatedly, I gave up and decided that Leopard has an unresolved bug that causes these symptoms on my old G4 iMac.. With the iMac going to Vintage status this month, I decided to reinstall Tiger on it, and it's future is now going to be life as a wireless print server.
I bought a new Mac Mini with 10.5.6 preinstalled. Since the new Mac has a lot of software installed that I won't use (print drivers, languages, Garageband, iWeb...), I did an Erase and Install on the first day, and used the Combo updater to go to 10.5.7. Within a few hours of use, with no 3rd party software installed, the hang I described happened again--the Mini showed the exact same symptoms as the old iMac. Thinking it may be something with the Combo updater, I did another Erase and Install, and this time used the Delta update to go to 10.5.7. Since then--about two weeks now--the hang has not returned.
As a side note to this, my parents own an Early 2008 iMac which shipped with 10.5.4 and was updated in March to 10.5.6 using the Combo updater. While helping them with it recently, it hung at restart--showing the same symptoms as my two Macs. This happened after they used it for about two months with no problems. I did an Erase and Install, and used Software Update to go to 10.5.7 (meaning the Combo updater was used). The hang hasn't happened again in the past two weeks.
With 3 different Macs now showing these symptoms, I'm convinced it's a Leopard problem, maybe something in the Combo updaters. I'm going to be updating my wife's Powerbook G4 to Leopard using a retail Leopard disc, and will have to use a Combo updater to bring it to 10.5.7. If the hang occurs with her Mac, I'll post a followup.