I think the key to your problem is the statement:

"Everything is working fine except on one workstation"

If you can't figure it out fairly quickly, the simplest solution may be to reload the software (image, or whatever you use).

There are a few things that I've seen cause this error.

1. Permission problems on the machine.
2. Something running in the background (startup)while KiXtart runs. You can synchronize the logon script and try to run it.. sometimes this helps.
3. Your script assumes something that isn't the case on this machine.
4. The KiXtart files aren't in sync (You have different versions in different places.)
....

I'm sure I'm forgetting something here.. but to troubleshoot, try:

1. verify all versions of kix by copying over fresh copies and deleting all other kixtart files but the ones you copied.
2. creating a dummy script with nothing in it and see if that runs.
3. Add the account of the user to the local administrator group and try it.
4. If those fail, try taking the script out of user manager and just running it locally from themachine.

This should get you started at least.

Brian