Last week I got some trouble to connect a Windows 2003 R2 32-Bit VM by using RDP.. I received this error:

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

To resolve this issue you can delete the “MSLicesing” key/folder in the register. Goto:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ , delete MSLicesing folder and reconnect the server.