Switching users freezes desktop

[Ranmadhu]

Keith Clark wrote:
> My desktop freezes solid when I switch to another user, do some work
> there, then logout back to my own desktop.  It does not ask for a
> password, but brings up the screen that I switched from and just sits
> there.  The only way out is ctl-alt-bksp. 
Which version of Ubuntu are you using? And do you have Compiz installed?

Ranmadhu