samba - Mar 2006 - Changed the IP address of Samba server, can't logon

After changing the IP address of our samba server (3.0.10), our users 
can't logon.  We use ldap authentication, which all worked fine for more 
than a year prior.  The samba log shows attempts as "guest" rather
than
the user's name.  Also logging in as root on an XP box translates to 
user guest, which is passed to LDAP and of course can't authenticate. 
I've removed the entries from wins.dat for all workstations and removed 
browse.dat from the DC.  I've removed the PC from the domain and added 
it back, still the same problem.  How and why is my username being 
translated to "guest"?

Thanks

Doug P