We ran into a fun little error with some workstations accessing a Remote Desktop Services session host via Remote Desktop Web Access. In a room full of machines, all setup with the same image, some of them would get this error when connecting: “The remote computer disconnected the session because of an error in the licensing protocol. Please try connecting to the remote computer again or contact your server administrator.”
This TechNet article as our exact error (http://technet.microsoft.com/en-us/library/cc756826(v=WS.10).aspx#BKMK_8). So we check the hosts, we check the licensing server, everything is OK. Some clients connect, some don’t. We reimage one of them, and it’s fine after that, so clearly it’s something in the client itself. Unfortunately, there’s a lot of machines and we don’t want to reimage all of them (especially if the problem comes back later).
I also noticed that the computers were getting a second login prompt after Web Access had handed them off to RDP. That doesn’t happen on our domain joined computers, but there the site is in trusted sites, and on these non-domain machines it was in the internet zone.
So I added the Remote Desktop Web Access site to the Trusted Sites Zone. Second login prompt disappeared, and the clients could connect. Success! We checked the machines that never had the login problem and the site wasn’t in trusted sites there, so it’s not a requirement, but if you run into this problem:
Add the Remote Desktop Web Access site to the Trusted Sites Zone. You get single sign on from RDS WA and you can avoid a client connection error.