Vista - Prevent users to save on Desktop

Hi,
I'm trying to prevent ordinary users to save files on the Desktop, but I
have some problem with Vista.

The users have roaming profiles.

I have made one startup script that creates a local folder C:\Desktop , and
set user rights to read and execute.

I have a logonscript that sets the User Shell Folder "Desktop" to C:\Desktop.

The redirection works, and for XP clients all seems to work.

When I log on to a Vista client, the profile wont load correct and the user
gets a temporary profile.

As far as I can see the Vista client doesn't add anything to the desktop at
logon, so I can't see why it fails for Vista and it works for XP.

Hope someone can help me whit this issue.