Unable to connect through proxy server

Hello, i'm trying to configure a proxy on a windows server 2008 machine. When I configure it (i used firefox connections settings, IE and a program called proxifier all with the same results) and try to open a web it keeps loading and after a while it says "connection timed out" Proxifier proxy checker connects to the proxy and the proxy responds but hangs when trying to connect to to google through the proxy. I tested the proxy on my linux machine and works without problems. Any idea on how to solve this?