hello
I just read this in another forum, the guy didn't reply back if it worked or not. so I assume it did. please let us know if it works as it may help someone in the future.
"Try this
In the User Accounts screen, click Change the way users log on or off.
Uncheck the box next to Use Fast User Switching.
Then, click Apply Options.
Do a reboot , then reactivate then do a reboot and try fast switching"