Out-of-date drivers and operating systems can cause a variety of issues, and are one of the first things to check when a game is having problems.
Minimum and recommended system requirements for StarCraft II.
Instructions for troubleshooting your network to allow Blizzard services to work properly.
Troubleshooting step for connection-related problems on Windows.
A guide for releasing and renewing your IP address and flushing the DNS resolver cache.