Only way to determine it that's the root problem would be to remove
gadmin-samba on all systems and see if sharing works any better.

Also have you installed Samba4 in place of Samba ? That package isn't
meant for production systems, not fully developed yet.

LAC> I wonder if there is a bug somewhere that causes gadmin-Samba to
LAC> fall back to unencrypted passwords if the connection times out?