Offline problem

Hello,
I'm new here, i'm from Lithuania, so my English is not the best, but i'll try to explain problem the best i can.

Situation.
1 Windows XPP, with all MS updates,
2 Domain
3 Static IP
4 Cisco VPN client (optional)
5 Offline Files.
6 Mapped drives on server where Outlook.pst is.
7 Several programs running from server (\\server\blabla\bla.exe)

So the problem is. PC goes "Offline", and as where is mapped drives mail stops working, and you get disc. from the programs you are running from server location, though internet connection is still up, and ping is reaching the server. Sometimes its happens after you use VPN client, sometimes just working... sometimes it happens few times per day, sometimes it happens 5 times per hour. I'm now checking several solutions, like mapping drives by IP address, it feels like something is wrong with NetBios, or problem with hub.

Maybe anyone had such problem, and could tell me what else i could do? Or maybe its the problem with the server itself, but, other users don't have such problems.

As usual, very few people look at the event viewer to see if any services stopped running or for any other conflicts. So, why don't you do that?

Actualy that was the first thing i did, the only event was. Its trying to become "Master Browser" with MS update and fix it started to behave much better, but problem still here... not that much as before.

I had that problem for a long time and couldn't figure it out. Finally while fixing something else I realized that my DNS server had some outdated forwarders. When I updated them, this problem went away.

I was thinking DNS as well but couldn't think of what.