First and foremost, I am not taking credit for the solution to this problem. What I am doing is restating the fix for remote desktop in hopes it will help someone else. Enough said – see below:
Recently I configured 2 new Dell Optiplex 755s for remote desktop using custom ports 3393 and 3394. I can do this in my sleep, so when it didn’t work, I was puzzled. Basically, you adjust the port in the registry, turn on remote desktop, add an exception to the firewall if enabled and you should be off and running. (Static the IP and configure port forwarding in the router for WAN access).
The weird part was that the remote desktop connection app would not return an error; it would quickly flash and sit there waiting for me to click on it again. I noticed that if I typed in the wrong port, it would give me a connection error, but ports 3393 and 3394 for their respective machines just flashed with no error.
We looked at group policies, network security, login accounts, etc. with no avail. A little Googling, however, returned the solution. The new Optiplexes both came with dual monitor capable ATI Radeon 2400 video cards. Apparently, there is a glitch in the video driver that ships in the new Dells. A quick trip to http://game.amd.com/us-en/drivers_catalyst.aspx to download the updated driver immediately fixed the problem.
I wonder how many IT support people have had to waste time on this problem with the amount of Radeon 2400 video cards Dell is currently shipping.
Update – May 14, 2010
This same problem occurred with an Nvidia 8800GTS video card using a driver from 2008. This computer had been working with remote desktop for at least a year on this driver and something recently caused it to stop allowing connections. Updating the driver, fixed the remote desktop as well. So apparently, this issue is rare, but not limited to Dell Optiplexes.