[Samba] Trouble in upgrading from 3.0.x to 3.5.x

[G N]

Hello all,

I upgraded to samba 3.5.4 from a working 3.0.x PDC in order to get Win7 
compatability.

After doing so, I can add machines (both WinXP and Win7) to the domain without 
problem.  Once I try to actually login however, I am told by
Win7 there there are no login servers to service my request, and by WinXp that 
the domain controller cannot be found.
The same XP machines worked with the same configuration on the old version.

I have checked the logs and there is nothing particularly alarming as far as I 
can tell.
I made the Win7 registry changes according to samba.org documentation.

A clue is that if I login to Win7 as a local account, map a network drive on the 
samba PDC, and then do a "switch user" and attempt 

to login to the domain, it then works.  If I do not do this step of mapping a 
network drive first, then it goes back to saying there are no login
servers to service my request.  I am mapping the network drive using the Netbios 
name rather than IP, so apparently Netbios name
resolution is functioning. 

Any help would be appreciated.

Thanks for your time.