To give the possibility to users to RDP a DC server, you should first permit them to log on locally to the domain controller:
http://technet.microsoft.com/en-us/library/cc785165%28W...
Once done, you should configure remote access to the server by enabling the normal user to RDP it:
http://www.facebook.com/video/video.php?v=1605350853911...!/video/video.php?v=1605350853911&oid=136667569684732
Moreover, The setting "allow logon through remote desktop services" only allows users to authenticate against the shared resources not to allow him logon to the server remotely. The user needs to be either RDP group or member of local admin which is default member of RDP group.
I hope I'm clear to you.