samba - Jul 2009 - Problems with shares after upgrading to 3.4.0

I'm running a lot of samba-servers (3.3.x) as AD members (security = ADS)
here and they are working fine. For tests I updated one of my server to 
3.4.0 and now have problems with lots of users accessing the shares..

Alltough there are still some users that always can access any share on
the updated server, most of them cannot. Running samba with log level 3
gives the following logs (only part shown)

Almost at the beginning of connection there is a difference at the following
call:

working client:
[2009/07/07 10:35:43,  3, pid=29169, effective(0, 0), real(0, 0)]
libads/authdata.c:302(decode_pac_data)
  Found account name from PAC: ATPCS7DC$ [ATPCS7DC$]

not working client:
[2009/07/07 10:27:26,  3, pid=28626, effective(0, 0), real(0, 0)]
libads/authdata.c:302(decode_pac_data)
  Found account name from PAC: SK17007C$ []

I don't know where this difference comes from but from here on the not
working
client (ok, the smbd for the non working client) behaves completely different
and finaly leads to the following:

[2009/07/07 10:03:17,  2, pid=10253, effective(0, 0), real(0, 0)]
auth/auth.c:320(check_ntlm_password)
  check_ntlm_password:  Authentication for user [sk1u05q4] -> [sk1u05q4]
FAILED with error NT_STATUS_NO_SUCH_USER
[2009/07/07 10:03:17,  3, pid=10253, effective(0, 0), real(0, 0)]
smbd/error.c:60(error_packet_set)
  error packet at smbd/sesssetup.c(122) cmd=115 (SMBsesssetupX)
NT_STATUS_LOGON_FAILURE

And that's completely strange as the user exists in AD and also is able to
access other shares on other servers.


As I've no idea now how to solve this, I'm kindly asking you for help...

Christian

--
"I sense much NT in you, NT leads to Blue Screen. 
Blue Screen leads to downtime, downtime leads to suffering. NT is the path to
the darkside."

- Unknown Unix Jedi