log off, restart and shutdown problem

[Guest knightwizard21]

Just recently upgraded from Windows 2000 pro to Windows XP Pro, and ever

since, we have intermittent problems of logging off, restarting or a shutdown

once logged on. I have disabled the "switch user" option ( did not work )

The only way that we can log off is to use the switch user button and then

restart the computer at the log on screen. Any help would be appreciated.