and, a little off topic, but
I bought a 17-55mm off ebay. It worked when I tested it, but the next day the AF went screwy. Just didn't focus at all, keep searching for focus. Checked everything, and was sure it was just the lens. Well, seller didn't take returns and kept saying something was wrong with my setup. Started a claim with ebay. and this is the part that doesn't make sense.
Ebay claims responsed that I needed to provide proof that the lens was defective within 4 days from an authorized repair center. WTF?
and the best part of that, there was no way to respond to them. The email stated to reply with questions and proof. I replied and they didn't respond.
Basically I got screwed. Sent the lens off to Canon, and they fixed it by replacing some board.
/off topic rant