samba - Feb 1999 - Samba 2.0.2, some users fall back to LanMan, some don't

We moved an smbpasswd file from 1.9.19 prealpha Samba to 2.0.2.  In both
cases, encrypted passwords are configured on.  Both Samba machines run
(ran) as the PDC. 

On the 2.0.2 machine, when some users login from a WNT 4 SP 3 machine it
falls back to the lanman password yet when other users login from the same 
machine, they don't fall back.  If I use smbpasswd and "update"
the (same)
password for the problem users, then they don't fall back to lanman. 

What gives?  Is there some (variable) incompatibility between the 
encryption used in 1.9.19 and 2.0.2???

Thanks,

David Mathog
mathog@seqaxp.bio.caltech.edu
Manager, sequence analysis facility, biology division, Caltech