Mapping a samba share from XP BIG problem.

Im hoping someone will have some ideas to help me resolve this

I have a win2k3 network and a 10.4 network. I followed the AD-OD integration doc (damn fine doc that apple themselves should have written ). Anyway I have all my mac user home folders stored on the mac server, and the windows users have their home folder redirected via group policy to point to this location as well. All works perfectly, then randomly after a while I get errors from our vb login script that state incorrect username and password when mapping a drive to the mac server. This occurs mostly after I've logged into an XP workstation 2 or 3 times. Mostly after a reboot I can log in and succssfully map the drives, but then after a few logins the error returns. All through this I can manually open the 'denied' share by using the UNC path from the run dialog box with no issues.
I've checked my smb.conf file and this problem still occurs. My DNS is set up correctly (DNS is running on Win2k3). On friday last week I removed the autoconfig lines from edu.mit.kerberos file and the problem stopped. But today (tues) it started up again. I've double checked my permissions on shares. I also reinstalled both the Win2k3 and OSX server multiple times. It seems that everything I try to resolve it appears to fix the problem, but a few hours later it starts up again.

Has anyone got any ideas, short of running 2 separate networks and doing away with integration? (unfortunately if I can get this solved I have to tell the school Im doing it for on thursday that it will be 2 networks )

HELP?