Can't connect to Steam Servers?

I am attempting to install a new pc game (Warhammer 40,000, Dawn of War 2, Chaos Rising) I enter my CD key fine... but when it tries to connect to steam it says: Steam Server is unavailable... Your computer is either currently unable to reach the steam servers or the service is temporarily disabled... Now I know the servers are working because steam is working on this same computer. I know it's nothing to do with a firewall because I turned my firewall off and it still didn't work and no third party virus protection programs are being used... Can someone help me out here? I'm getting really frustrated lol Thanks