20 inch Aluminum iMac crashes after installing Mac OS X Combo Update 10.5.6

Question

I have a school lab with 22 of the new 20 inch Aluminum iMacs. They all have been having a problem with crashing after someone logs onto my network server, which is still running the 10.4 Tiger version of the Apple server. They run fine if you boot up and log on as a local user, and they seem to run fine when you boot up and log on to with a server account, but when you log off from the server, about five seconds later while the aurora screen is still showing, they crash and give you the Apple version of the "blue screen of death."
I was told that the fix was to download the combo update separately from the Apple website and use that to reinstall and update the operating system.
I downloaded and tried installing with a 10.5.6.dmg file and a 10.5.6.dmg.smi file, but they both crashed.
Where can I find the "fixed" version of this update or is there some other fix?
I have tested this on 9 or 10 different systems.
The first file was MacOSXUpdCombo10.5.6.dmg, which is a disk image file that is 668.8 MB or 684,774 KB.
I looked in the discussion groups on the Apple web site and found some discussions for problems that seemed similar to, but not quite the same as my own. They led me to a file MacOSXUpdCombo10.5.6.dmg.smi, which a self mounting image file that is also 668.8 MB. I tried it and got the same result.
I can install my dvd, which gives me 10.5.1, which will log off and reboot correctly.
I can then install several miscellaneous upgrades:
Pro Apps Update 2006-02 V1.0
AirPort Utility V5.3.2
Remote Desktop Client V3.2.2
QuickTime V7.6
iTunes V8.0.2
and also
Front Row V2.1.6
The system will then log onto the network, log off and reboot correctly.
But, when I install the 10.5.6 combo update from any of my sources, it boots and logs on fine. But, if I log onto the network, it crashes when I log off.
Where do I go from here?
Thanks for your help.
John R H

Answer 1

Have you tried starting up with your install disk and doing a disk repair?
Put the install disk that came with the Mac in the DVD/CD drive and restart holding down the 'C' key. You can take your finger off once you hear it making noises from the DVD/CD drive. You'll be presented with a screen where you choose your language. At the next screen on the menu bar select Utilities>Disk Utility you then select your Macintosh HD on the left and click on 'repair disk'. If it makes any changes click on 'repair disk' again and repeat the process until you get a clean pass. Once done select restart from the Apple menu and hopefully the Mac will boot normally.