I'm at a college where they use a proxy server to connect the computers to the internet. They have this server configured to block all ports besides 20, 21, 80, and 443. When I look at my Comodo firewall connection list, though, I see that Minecraft is trying to connect to minecraft.net on port 80, which should be allowed. I've configured Java to use the proxy server, so I'm not sure what the problem could be. The in-browser version of Alpha as well as Classic work fine (Multiplayer doesn't work, but that's because it doesn't use those ports).
Is there any help for me?