yep, I got same here, I read lots threads and it was suggested following, I did them all and still same, I am working on the java update one and hope that will work.
this is my thread hope that help u, well it did help me
OSX cannot shutdown restart or swicth user
Hi, folks
I have switched from PC half year ago and my experience with OSX is very good so far.
One day I came back from work and my wife told me our imac G5 is freezing,
I took a look and did a shutdown by holding on the power button.
After that it stucked in a blue screen, and I did a few times hold power button as that is my only choose, it was not helping.
Therefore I decide to do the PC way, take out my OSX disk and did a re-install with keeping my previous user profile.
It login ok after that but I notice two issue is happening
1. I cannot switch user by clicking the username in right top corner, and it turns to the color ball forerver.
sometimes it works if u just login but after a good mac use 30 mins, it will not be able to switch user as above described.
2. I no longer can do restart or shutdown from finder
after I click on it, it just do nothing, no color ball, no CPU high, just nothing
However, I can do shutdown from terminal, and sleep and force to quit is working from finder.
I notice shutdown problem is happending after I did a onyx and onyx is able to shutdown mac after did a scan.
3.while I doing update I see some red process hang and update cannot complete, but I am not sure which patch I am updaing.
I have a feeling this is the root of all this three issues, as I kind of remember I was updating before this all happned.
BTW, I am a very heavy BT user, not usre this helps or not.
Following is what I did so far
re-install OSX with keep user profile(twice)
fsck repair
nvram reset
removed com.apple.finder.plis, com.apple.sidebarlists.plist
Someone suggested to delete the folder 'Quickbackstartup' (part of 'speedtools')in the startupitems folder in the Library folder.
However, I cannot find that file.
I am using Imac G5 1.8 10.3
many thanks for viewing my threads