Blank screen after LOGOUT

[Alessandro Torrisi <alessandro torrisi eurone it>]

Hi ! I've got a problem with my FC 2, very very strange.
I use KDE and when I logout to GDM nothing appears in my LCD screen...
Then I power-off the screen, and after some minutes (probably ten minutes) I 
power on the screen and my login screen is BACK !!!
Probably a timeout ??? What is happening ? The same thing when I switch from a 
TTY to another !

Please HELP ME!!! 
Best regards, Alex..