Impossible to connect to a Windows Server 2003

I have a WXP pro sp2 client in a windows 2003 domain with 2 WindowsServer 2003.
Sometimes i can’t connect to my primary domain server but i can continue connecting to all other servers and clients (XP, NT, 2003).
I’ve tried to change my client name and to unjoin the workstation from the domain.
The strange thing is that i have 2 network interfaces, normal and wifi.
When i was disconnected with one of them i can change interface and connect with the other….all it’s ok for some minutes and then, again, i was disconnected.