OK, sounds like an issue on your end, more specifically, something is blocking the games from connecting. I'm guessing it's probably a firewall, do you have one? And if you don't, you still have the Windows Firewall. The fastest check you can do is when you open the game and try and find a game, or even better, try and join a game, just hit Alt+Tab and see if there is a popup saying something like "So and so blocked this application from connecting to the Internet, do you wish to unblock it" or something vaguely to that effect. One firewall I used was really infuriating, as it came up with this pop up but cleared it if you exit the game, so I went in there, couldn't connect, hit exit to check if things were working fine and missed the message. You can also try disabling Windows Firewall [http://windows.microsoft.com/en-za/windows/turn-windows-firewall-on-off#turn-windows-firewall-on-off=windows-7], I personally do it just to be safe (yeah...the irony). Just check to see if that fixes anything.
An alternative cause is likely to be your router, although, I don't know why this would crop up suddenly. There usually needs to be some changes made, say, getting a new router or mucking about with the settings of it.
