Are you running a proxy program? If so, disable it.

Spyware/Maleware could of added a proxy setting;

Goto, Start, Control Panel

Internet Options >> Connections Tab

At the bottom, Local Area Network (LAN Settings)

Click on the button;

If: Automatically detect settings is 'Checked', Uncheck it.

Proxy server:

Probably enabled, remove any IPs and ports and uncheck all boxes you see in the proxy area.

Press, Ok.

Apply and Ok.

Try your browser.