Pc hanging after "log off"

>I have an odd problem with my Fujitsu Siemens Scaleo 600, XP-Home SP2,
>after a new clean XP Home re-installation.
>
> When user is trying to log off "Start/LogOff", the PC screen goes randomly
> into black (not every time) and I cannot longer make contact with it. Even
> keyboard is not reacting (NumLock and CapsLock). But some how the PC is
> still up running, because I can se the harddrive light flashes every now
> and then! The only way to connect again is to push the power button until
> the PC reboots again.
>
> If using Win and L button, the PC is back on the "Logon screen" and there
> is no problem logging on again.
>
>
>
> I never experienced this before I took this clean XP re-install, so
> guessing this has to be some settings or driver problem?
>
>
>
> In the beginning I thought this problem were related to my GeForce4 Ti
> 4200 graphic card, so I tried the driver which I used before and are now
> running the latest driver, but still the same.
>
>
>
> My screensaver setting are:
> Screen saver:
> Wait 40 minutes on resuming, display Welcome screen
>
> Screen saver/Power Option properties
> Turn off monitor Never
> Turn off hard disk Never
> System standby Never
>
> ....Advanced:
> Prompt for password when computer resumes from standby.
>
> Is there anyone out there to give me some advices or tips on what to do
> now??
>
>
>
> Kindly regard,
>
>
>
> Pvest
>
>

> Check under Control Panel | User Accounts, Change the way user log on or
> off.
> Make sure that Use Fast User Switching is checked.

> Also make sure that under SERVICES.MSC, Fast User Switching Compatibility
> is set to Manual and is Started.