samba - Oct 2007 - could not read attribute 'gidNumber'

Hi

I am using samba 3.0.23c on RHEL5 with security = ads. If I use "idmap
backend = ad" i can see in the logfile that it gets my uidNumber:

ad_idmap_get_id_from_sid mapped SID [S-mysid] to POSIX UID myuid

but it is not able to get my gidNumber:

[2007/10/04 09:44:17, 1] sam/idmap_ad.c:ad_idmap_get_id_from_sid(309)
  ad_idmap_get_id_from_sid: ads_pull_uint32: could not read attribute
'gidNumber'

any idea?

thanks!