I had this problem on a Windows 8 RTM installation in a domain environment. A domain user was able to log on locally but not through Remote desktop. Another domain user was able to logon both locally and through Remote desktop. Computer has Network Authentication Layer (NLA) enabled. I turn of NLA, and both users can logon Remote desktop.
The first user had a "Allow only logon to these workstations" setting on the user object in the domain. Even if the computer name was added to the list, in a Remote desktop scenario it would not allow logon.
So I changed the user object in the domain and allowed the user to logon to any computer. Now he's able to logon using Remote Desktop, even with NLA turned on.
Guess it's a bug in Windows 8 RTM.
Regards,
Krug