samba - May 2007 - group mapping

Hi all

If i add something like "myunixuser = MYDOMAIN+domainuser" to my
username.map ist works. but if i do the same with groups ("myunixgroup
= @"MYDOMAIN+domaingroup") i can no longer map  my samba shares...

any idea?

what is the difference between "./net groupmap ..." and using a
username.map?

thanks for your help!
urs