[Samba] wbinfo -a fails plaintext auth; passes challenge/response

[Mike Leone]

Once again, I am trying to add a machine to my Win2003 AD (that has
Services for Unix installed). I am using Xubuntu 9.10, and samba 3.4.0.
I set up Kerberos, and am getting a ticket. I have successfully joined
the domain.

# net ads join -U administrator
Enter administrator's password:
Using short domain name -- DACRIB
Joined 'DUAL-BOOTER' to realm 'DaCrib.local'

wbinfo -u does return all users, both local and AD.
wbinfo -g returns all groups, both local and AD.
wbinfo -t succeeds.

However,  I am failing plaintext authentication, with wbinfo -a:

 wbinfo -a turgon
Enter turgon's password:
plaintext password authentication failed
Could not authenticate user turgon with plaintext password
Enter turgon's password:
challenge/response password authentication succeeded

Google seems to be non-helpful, with this failure message from samba.

Can anyone shed any light on my problem? Eventually, I want to configure
this machine so that I can log into the machine using only AD accounts
(no local logins), but I didn't want to proceed, until I had this
problem solved.

Thanks