Introduction

This one is not immediately obvious. Suddenly a connection that was working fine just stops and all that you get is a generic error message.

Fix

The fix however is simple. Just remove the following file from your home directory

rm ~/.freerdp/known_hosts

That's all there is to it. Thanks to the Ubuntu forums for the answer: http://askubuntu.com/questions/157723/cannot-rdp-to-windows-7-with-remmina-on-12-04