30 second delay connecting with XP Professional to Windows 2003 file share w/ AD

I have a small office network connected via a Dell Power
Connect switch and Cat 5 cabling throughout. I can
connect to my Windows 2003 Server file share quickly and
easily through windows explorer on my Windows 2000
machines, however, on my Win Xp Pro machines in my office
there is a 30 second delay every time I access my file
share. The hour glass sits there for 30 seconds and then
finally connects and works fine. The transfer speeds are
very quick once connected. On all of my desktops the two
IP address of the server are the first and second
addresses in DNS, followed by the ip addresses of my ISP.
What can I do on my XP machines to remove the 30 second
delay and not allow the connections to timeout. Thanks.