general OS bug or particular kext issue?
First off, wanted to add a "me too" on the 10.4.8 mac pro hang on restart/shutdown issue, and thanks to phreaky for tracing this to kextd. It's been frustrating to have the XP side of my machine behaving better than the OS X side.
I recall there being a pretty nasty kernel panic issue with the CiscoVPN and Parallels kexts in 10.4.7, so I'm wondering if this is related.
- - - -
After uninstalling the Parallels kexts (helper,hypervisor,Pvsnet,vmmain), my machine no longer hangs on restart or shutdown. I should note, though, that a) I don't think I was using the latest version of Parallels, b) this might not be Parallels "fault", per se, and c) I also ran a disk permissions repair (although it didn't seem to find errors in anything that *looked* related).
ymmv