If you’re using GitHub for Windows in a corporate, chances are high that you’re behind a big bad Corporate Firewall/Proxy. GitHub for Windows doesn’t yet have the proxy parameters in its GUI for setting Options.
To configure GitHub for Windows to use your  corporate proxy, edit the .gitconfig file typically found at C:\Users\<yourusername>\.gitconfig or C:\Documents & Settings\<yourusername>\.gitconfig
Close GitHub for Windows; In .gitconfig, just add
[http]
proxy = http://dumbproxy.yourcompany.com:8080
[https]
proxy = http://dumbproxy.yourcompany.com:8080
And speaking about dumb proxies, take a look at the category this proxy spews out as the reason for filtering it out 🙂
