I had a problem recently when I couldn’t RDP to a windows 2008 R2 server. The server’s RDP connections are secured by a certificate, but apart from that its a normal server. Each time I tried to connect it failed before getting to a login prompt. This normally always points to a problem with the network level authentication (The certificate bit).
I did some googling and found an MS article (KB2001849) which didn’t quite fit the problem but had the solution. Some how the permissions for local account NETWORK SERVICE on the certificate securing RDP has been lost. The steps from the article on how to resolve this are
This allowed me to get to the login prompt, but any credentials I tried were rejected. I knew this was still related to the Certificate as I couldn’t see any RDP attempts (failed or otherwise) in the event logs. So I reselected the cert for the rdp connection using the below steps
a. Click Start > Administrative Tools > Remote Desktop Services > Remote Desktop Session Host Configuration.
b. Select RDP-TCP in the Connections window, right click and go to Properties.
c. Click on the select button at the bottom and choose the certificate
d. Click ok and ok again and you will now be able to log into your server