Cannot disable offline files

I have an SBS2003 network, and installed all the updates for Vista support.
I previously created a Group Policy for computers to disable the use of
Offline folders for my desktops. It works fine for all my XPSP2 desktops,
but my new Vista desktops show the Offline files "States" is enabled and the
option is greyed out.
The redirected folders (My Documents) are all synchronizing.

I then created another GPO for the users to enable the "Do not automatically
make redirected folders available offline", but still the option is enabled
and greyed out.

The GPO locations I have configured (and work fine for XP) are as follows:

Computer Configuration -> Administrative Templates -> Network -> Offline
Files
Disabled the "Allow or Disallow use of the Offline Files feature"

User Configuration ->Administrative Templates -> System -> Folder
Redirection
Enabled the "Do not automatically make redirected folders available offline"

Is there another location that I should be looking at?

Thanks for your help