samba - Oct 2004 - Post SP2(?): Login as administrator

Hi,

I installed SP2 on a winXP machine (Samba 3.0.7, PDC/LDAP).
Now when I login as a domain administrator the machine will  reboot.
No problems logging in as a user or as a local administrator.
No problems connecting to a network resource as a domain administrator.
Nothing in Samba or XP logs.

Other SP2 machines in another Domain (Samba 3.0.7, NT4 Domain), have not 
such issues.

Is this an SP2 or Samba issue (or combination thereof)?

Thanks

Gil