Yeah, I checked PIA out. My bad, they're a VPN server. Their hostname isn't too subtle, though (proxy-*.privateinternetaccess.com), a simple whois and any site that wants to filter out proxy users can catch you.

Could you check whatsmyip.com (just visit it) and see if it shows that you're using a proxy? If it says that you're using a proxy, try VPNbook. If it says No Proxy Detected, then I'm stumped.