XP Pro disconnecting from network

I have a Dell Optiplex SX260 that was at a branch office joined to a domain. We moved it from that office to our main office and tried to connect it to our domain there. We renamed the computer and put it on a temporary workgroup and then joined the domain, set up local users, reinstalled programs, etc. The problem we have is that everything works for about 10 minutes and then it loses connectivity to the server. The mapped drives and applications all stop working and we need to reboot. We dont see any errors or anything.
What would be causing this? How can we fix it?
Thanks for any help,
johnny5

 

I turned that off, but it seems that the disconnect happens even when working. I was just logged into it from another computer in the office over remote desktop and all of a sudden it disconnected when I was looking at the event log.
The event errors I saw were an intermittent "no domain controller available" and the "mrxsmb" warning that happens on most XP machines after SP2, and W32time (where can I just turn that off or make it go away...) but as I was working it dropped connection and I cannot reconnect.

 

Disabling and re-enabling the ethernet connection in "network connections" will restore connectivity temporarily. Then it disconnects again after a couple minutes.
Any other suggestions>?

 

I made the IP static and ran the command "net config server /autodisconnect:-1" per mskb http://support.microsoft.com/default.aspx?scid=kb;en-us;138365 and it seemed to work ok until someone ran AdAware and Antispy on it and now it is disconnecting every 10 minutes again, with no warning or error message. Does anyone have any ideas or solutions for this type of issue?