Removable Storage Access

Hello,

I have an issue when I apply the following GPO :

User Configuration \ Administrative Templates \ System \ Removable Storage Access \ All Removable Storage classes: Deny all access.

When I set this to enabled all users still have access to USD, CD-ROM's etc.  The security filtering on the GPO is correct.

However if I set the same Computer related policy setting the devices are locked down for all computer accounts.

I need to set this for user accounts and not computer accounts.

Does anyone know why this setting doesn't work when set under the user portion of group policy ?

The OS is Windows Server 2008 R2.

Thanks