Connecting my old WFW system to Redhat 5.2 I found that I was able to login without the having the same domain name. It actually doesn't mather what domain name is chosen. Access is always granted. I suspect this is a samba problem, but I'm not sure about it. I used both the samba-1.9.18p10-3 and samba-1.9.18p10-5 RPMS. Both acced the same way. A reply about this problem whould be nice.
This appears to have been a samba bug; it was just fixed in the latest samba release (2.0.4); RPMS will be in the next Raw Hide release. If you need a 5.2 package, you should be able to recompile the source RPM.