well i'me stumped then, this may sound drastic but wiuld a windows re-install cure it
What have you got runnig
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www.altavista.com for
Fast User Switching troubleshooting
go to control panel, admin tools & services
Locate terminal services & check to see if its on manual
Locate fast user switching & check to see if enabled
Did you apply changes before closing the user acounts screen
Have you tried e-mail microsoft directly