The following error was experianced when logging onto a citrix server using a standard user account with RDP. Administrator accounts can still logon with RDP.
The desktop you are trying to open is currently available only to administrators. Contact your administrator to confirm that the correct settings are in place for your client connection.
Also the error message "To log on to this remote computer, you must have Terminal Server User Access permissions on this computer."
The second error is ususally when you are trying to log onto a terminal server and you do not have "Allow logon over terminal services" user rights assignment in place. Most cases you nest the user account or domain users inside "Remote Desktop Users", a group that is always granted "Allow logon over terminal services".
However with citrix installed even though these permissions are right it will still not log in. To resolve this go to tscc.msc to open up the Terminal Services Configuration Connections. Go to the properties of the RDP-Tcp terminal services connector. Go to the Citrix Settings tab, and untick Non-administrators only lauch published applications.