Your Internet connection is either very poor or is not processing UDP packets
-or-
Unable to connect to Battle.net

• Check with your Internet Service Provider (ISP) and/or network admin to make sure your network is not restricting UDP or TCP/IP packets on Port 6112 of your router.
• If your ISP has a program you need to install before connecting to them or the Internet, make sure their software is a 32bit version.
• If you are using a modem make sure you have the latest updated drivers and that your ISP supports this connection speed.