May 272009

Sometimes when you try to start a Remote Desktop Session (RDP) from your Windows 7 computer you may end up with the following error:

“Because of a protocol error, this session will be disconnected. please try connecting to the remote computer again”

You may find that you can connect to this system from a Windows Vista or a Windows XP computer.

I haven’t seen a bug reported or assigned for this problem in Windows 7. But, a quick workaround would be rename the file c:\system32\mstscax.dll file on your Windows 7 computer and copy the file from a Windows Vista system.

If you do not have access to a Windows Vista PC, click here to download the file and upload to your PC (c:\windows\system32)

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  5 Responses to “Protocol error in Windows 7 RDP connection”

  1. I’ve tried this, but with no luck. I get an error message back that states the current Remote Desktop ActiveX Control (mstscax.dll) is not valid. Any other suggestions?

  2. Wouldn’t mstscax.dll need to be re-registered?
    Is it only this dll that needs to be replaced? What about mstsc.exe?

  3. I’ll comment that the workaround of substituting RDP ver. 6.0 for the 6.1 native in Win7 will likely work for some connection problems, but simply replacing the files (you may need two files from System32: mstsc.exe, mstscax.dll ; and two from en-US: mstsc.exe.mui, mstscax.dll.mui) BREAKS THE WINDOWS 7 XP MODE VIRTUAL MACHINE, so use with care! As a workaround for the workaround, leave the original RDP programs in place, and set up a new folder with the ver. 6.0 exe and dll, and a new subfolder in that called en-US with the ver. 6.0 mui files, and run the exe from that location as needed (Options and Open will let you select previously-saved RDP connections). –sigh– sure wish Microsoft would get on this one!

  4. Randy Smith has this spot on. Good workaround.

    Oh and Microsoft why is it 10 months on new win7 machines are still shipping with this problem?

  5. When opening my RDP client, I kept getting

    “remote desktop connection has stopped working”

    Here is the mstscax.dll from a working Windows 7 SP1 32BIT PC that fixes it

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