Check the following blog http://blogs.technet.com/b/askds/archive/2009/03/12/how-to-properly-disable-offline-files-in-windows-vista.aspx. What if worked for me is this part:
"To enable/disable Offline Files via WMIC:
We use the Enable method of Win32_OfflineFilesCache to enable or disable offline files. Simply pass the Enable method a Boolean value.
Execute the following command from an elevated command prompt:
wmic path win32_offlinefilescache call enable false
... a reboot is required for the new setting to take effect."
It worked for Windows Vista, too.
