Windows 2008 R2 Standard Remote Desktop Users cannot Connect

I have a windows 2008 R2 Standard Terminal Server and some users aren't able to connect even though they are in groups that are in Remote Desktop Users on the local computer.  I checked the local security policy setting "Allow log on through Remote Desktop Services" and I see that Remote Desktop Users is a member of this group.  Inside of Remote Desktop Users we have DOMAIN\Domain Users and DOMAIN\Terminal Users.  Most of our users are in both groups, but there are still some people that aren't able to connect via Remote Desktop to this computer.  There are no users in "Deny logon through Terminal Services."

Thanks!