Cannot Connect to a Game-Server!

Since my Laptop got repaired (new Mainboard) I cannot play Crossfire because if i choose any Game-Server it says: Connecting to Server...
Please Wait.
10 minutes later: Connection Failed.
The same System-Settings as before, same Firewall, same Internet. Don't say: Turn Off your Anti-Virus program. That doesn't help!
If you know an answer that maybe can help, post it here.
If you don't know an answer that maybe can help, get out of here!