How the hell are they tracking me, is my proxy leaking?

Sounds like they issued a Cblock Block on you. Very easy for them to do because squids do come back as a proxy connection. So If they block the whole Cblock their only blocking known proxies.. Seen it alot.

P.S. Tagged is big for that crap

Very informative answers from you guys. I guess that kind of shatters the feeling of safety I have when using private proxies.