[Samba] Problems with BDC-Samba starting with version 3.0.25

[Thomas Blank]

I'm running Samba on Solaris 10 Sparc for about one year now (version 3.0.22 and then updated to 3.0.24). It acts as a BDC.
Now, after updating to 3.0.25c some users cannot log in.
I'm getting this error:
  domain_client_validate: unable to validate password for user myuser in domain MYDOMAIN to Domain controller MYPDC. Error was NT_STATUS_NO_SUCH_USER.

The difference between the users is, that one are working on a desktop computer logging in to the domain on startup, the other ones are working on a notebook not logging in to the domain initially. They use local username and password matching the entries in the domain.

No problem so far with 3.0.24 - connecting the shares worked fine. Starting with with 3.0.25 it fails.
If I connect the share manually using "net use X: \\mysamba\myshare" and specifying "MYDOMAIN\myuser" and password, it works.

What has changed? What am I doing wrong?
If you need the config and/or build options, let me know.

Thanks for your help!
Thomas