an error with login as Remote Desktop User, Win server 2008 R2

I am working with linux and using Remote Desktop Tool to connect windows server 2008 r2, but failed. I do not understand this error.

Error:
"To log on to this remote computer, you must be granted the Allow log on through Terminal services right. By default, members of the Remote Desktop Users group have this right......."

But the User is already a member of RD Users group!