COH A NAT negotiation error
 

I have purchased the company of heroes along with all the expansion through steam. Problem is though I can see others in multiplayer but can't connect, the error message is "A NAT NEGOTIATION ERROR OCCURRED". Funny part is when I use my other connection which is dongle based with 3G speed, it connects and I can play as long as I wish.

Firstly, you should be on the Steam forums for this.
Secondly, its a Firewall issue. A firewall is blocking the connection, you will possibly also need to open a few ports for the game as well.

Google your error, you will find many answers for your problem. ;)

actually firewall is turned off while playing, but I found that the new steam version does not suffer from this, so this post may be closed.