Let me first explain how the network is set up.
Main Office: VPN Router > Switch > SBS 2003 Server (only DC)
Each of 7 Branch Offices: VPN Router > Switch > Clients (all running XP, all either SP2 or SP3)
Each of the branch offices has an ipsec vpn tunnel into the main office. The DNS setting on each of the clients points only to the SBS 2003 server at the main office. When the users log on group policy is applied and their documents/desktop/application data are redirected to storage locations at their respective branch offices.
Now, I've added a filtering machine (running Untangle in bridge mode) to the main office. It is only filtering for viruses, spam, phishing, inappropriate content based on categories. No protocol filtering or intrusion detection.
New Main Office network setup: VPN Router > Filtering Computer > Switch > SBS 2003 Server
All of a sudden when people started logging on today from the remote sites (first day with the filtering computer in the mix), they are getting stuck at "Loading your personal settings" and it will hang there.
I remove the filtering gateway and everything goes back to normal. Clients that never logged off last night had no problems during the day (exchange mail worked in Outlook, could browse shared on the SBS 2003 server, etc).
So I guess my question is, what would cause logons to fail at "loading your personal settings" in respect to the filtering computer? What is is blocking that the clients need?