Here I am having an interesting problem. for all time never met a error when running RDP.

Failed to find file C:\\Windows\\system32\\mstsc.exe.MUI

The solution was simple...

When you start the remote desktop client mstsc.exe I get the following error message:

[Window Title]
mstsc.exe

[Content]
The system cannot find the file specified.

C:\\Windows\\system32\\<LANG_NAME>\\mstsc.exe.MUI

[OK]

the command is mstsc.EXE.mui there is a mui in EN-EN, en and en-US folders. I updated mstsc to version 6.3.XXXX next KB2592687.

If you have another method or this did not help. I will be glad for more advice.