HP Proliant with MS SBS 2003 R2 - Can no longer connect XP Pro clients

[DCGSyd]

Can no longer connect clients (local or remote) running XP Pro to HP Proliant ML110 G4 server running SBS 2003 R3 and cannot ping server from clients.

From server can ping clients using IP address but not by host name as old ip addresses come up on ping request.

Was able to connect prior to installing MS auto updates and could use web access from remote notebook client plus get e-mail from Exchange server via MS Outlook 2007 on this notebook.

Server sits behind Netgear FVS318 VPN router and server plus clients are running Trend Micro WFBS 5 Advanced.

Now, the only way that clients can get internet and Pop 3 e-mail is to enable DHCP on router and take HP Proliant ML 110 G4 off the network.

Can anyone point me in the direction of a solution please?

Many thanks