A few things to try

Cycle the power on both cable modem and wireless router

Open a command prompt and type: ipconfig /flushdns

Disable antivirus and firewall before launching the game

Disable ALL torrent applications on your network

Try connecting directly to your cable modem

If your using wireless, try using an Ethernet connection instead

Change your dns servers to something different tha what they are now, ie 8.8.8.8 (google dns)


I'm not making any assumptions as to what could be your specific issue, rather these suggestions would be a good place to start and help you narrow down what's causing the issue.