actually, the anonymizer WEBSITE I assume you mean, has had their IP records scrutinized by the FBI, several times, because they assume if you are using it you are up to no good (fraud or porn), per several news stories I have seen - and no I dont have links - I cant keep everything I stumble onto.
I have really gone thru all the proxy stuff like proxy chains and tunnels etc., but have found only one thing that works easily and is anonymous - that's surfnow
http://loomsoft.com/
All the other anonymizer software uses a proxy server service to connect to at the company that sells the sw - so once again, all your travels are logged.
Surfnow does a quick search for high anon proxies and fairly quickly tests them for speed, or you can add your own proxylists to try.
these guys use a little java to show just how open your info is
http://www.danasoft.com
And FWIW:
A guy I know got caught downloading the last Star Wars movie on the internet (during release), and his IP provider shut him down for 2 weeks, telling him that any further violations would mean permanent shutoff of his service and legal action. The funny part is that he was using a high anon proxy at the time. So he called the IP support line and went to a level 1 techie, who was quite friendly, and spent about 30 min talking to him about how in the hell they found his IP address using a high anon proxy. Well, as it turns out, in post 9-11 America, there is no way to hide your IP address anymore, no matter what you do. They have 35 ways to find out who you are and what you are doing - phone/cell phone/FAX/internet/email. Whether you believe that or not is of no consequence to me, I have proved it to my own satisfaction - and thats all that counts.

Yeah, you can use a proxy to relog in to something like AT after a ban, but you will not hide from someone who really badly wants to know who you are.
Those days are over.
Trust me.
Your only real option is to move to a country like Russia, where, even if they do find you, nobody gives a crap about what you did anyway.