Offline Files - Sync Centre always shows 'Sync Pending' but nothing happens

[smarter]

Can someone please help?

I have a Dell Vostro 1700 laptop running Vista Ultimate with SP1 applied, which I use to sync up with my companies shared folder via VPN on an SBS2003 domain.
This all worked OK from setup 2 or 3 months ago but for some strange reason has now stopped working. I have tried disabling and re-enabling 'Offline Files'. I have re-initialised the offline cache using the modify registry method but niether have worked.
I have mapped the remote company folder to a drive letter and when I right click and select 'Always Available Offline' I get a brief message saying 'Completed preparing files so they are always available offline' but if I right click again it hasn't stuck. Same thing if I get 'Properties' of mapped drive and select the 'Offline File' tab then tick the 'Always Available Offline' check box then OK - re-open 'Properties' - 'Offline Files' tab the check box is unticked.
Viewing the disk usage from the 'Offline File' control panel both 'Offline files' and 'Temporary files' are at 0 bytes. Sync Centre shows no errors but does show 'Sync started' and 'Sync completed' within a minute of each other. Needless to say nothing has synced and I have no files to use offline.

If anyone has any ideas, they would be much appreciated.

Thanks
Steve