• We have updated our Community Code of Conduct. Please read through the new rules for the forum that are an integral part of Paradox Interactive’s User Agreement.
My guess is you have moved the game to a different directory than you originally installed into, so the registry points to a place that doesn't exist. If so you may have to do a complete uninstall/reinstall to the place you want the game to be.
 
Have you gotten this problem figured out yet? For me, this message usually means that the host has blocked the ports (1630-1638, I think) that the game uses.

In any event, we are starting a new MP game tomorrow, March 5, and are looking for some new players. If you are interested, see the Rise of the Minors thread. We'll be playing from 6:30 to 9:30 pm est (GMT-5).