[Samba] Samba problems with versions >= 3.0.25b

[Masopust, Christian]

Hi all,
 
I had a samba-server as a member in an Active Directory (security = DOMAIN)
running 3.0.24 and everything was fine (system is RedHat Enterprise 4).
This server is in domain "A" and all my users accessing this server are in
another domain "B" (with trust relationship between A and B).
 
During the latest RedHat updates I got a newer Samba-version (3.0.25b) and 
the problems started.
 
>From time to time no user from domain "B" can access shares on my server!
 
ok, so I decided to update Samba to the most recent version (3.0.27a, "self-built"
packages with "makerpms.sh") and the problem is still the same!
 
So the only possibility I have is currently downgrading the Server back to Samba 3.0.24.
 
Any Idea what changes this problem could cause?
 
thanks a lot,
christian
 
P.S.: as this is a very busy life-server I currently have no possibility to make traces
         with version 3.0.25b or above... but if really neccessary I could stop it for some
         time to get the needed traces (please tell me which "log level" is needed...)