RE: Dynamics GP2010 - local workstation can only log in as 'sa'
I think we are missing some of the details that make an answer difficult.
When you say - created new user on the work station - what kind of user? Did you do this in Active Directory? Did you do this on the application Users?
If you created the user in the Application - Users - did you also provide User Access - which tells the system what company they have access to.
If you did the above, did you forget to grant Security to the user for each of the companies that the user has access too.
It also sounds like from the limited comment that you have a permission problem - user can not access files on the terminal server or they can log onto terminal server, but can not run application on the machine. Security / Permissions are a huge part of the problem for all user issues.
If this helps, mark as Answer. But it would be helpful to get more details to assist in more detail.