I having problems from our server that loses ip addresses. I had them as static and then one user who vpn on to our network actually took the server ip address which meant know one can access the files on that server.
As this happened i decided to reserve the ip address in DCHP but this morning it has happend again but this time no one seem to have taken the address though.
I'm not sure if this help but the Xp users can still see the filres on that server when the ip is lost but the windows 7 users cannot.
Windows 2003 SBS version