Still Getting Blocking Issues 6.6.3

[Richie_OLSJ]

Ok, we are still getting issues when ANY web/app blocking policies are enforced. It is an easily replicated problem.
Clients: Windows XP SP3 with latest updates
Windows Server 2008 R2 Active Directory Domain
Firewall active, but ABTutor exceptions in place (5151,5152)

Scenario:
A WEB or APP BLOCKING policy (usually WEB) is applied on an ICT suite (around 25 pcs). SOME pcs (not always the same ones) will get the following (whilst others work as normal):
- No GPO policies applied (redirected folders, start menus, desktop wallpaper)
- some will get their redirected My Documents, others won't

Log the user off and back on again and it might work, or it might get the above again.

clear the BLOCKING policy, log them off and back on again (doesn't need to be a reboot, just logoff) and they will always log on correctly.

Any help, solutions or ideas for further investigation very much appreciated

Thanks,
Richie