Phinsup: One of the things you learn to do after one or two incidents like this is *save the receipts* for your big purchases. You'll never be sorry if you do, but you'll often be sorry if you don't, and you'll have no one to blame but yourself.
I had an experience very much like yours with AppleCare five years ago. I hashed things out over the phone with them, and eventually it became apparent that with my aging eyes, I had mistakenly substituted an "S" for a "5" (or vice versa) in my computer's serial number when I registered it. The result was that when I bought the AppleCare Protection Plan several months later, my Powerbook wasn't in Apple's registration database under its correct serial number, so I couldn't register my APP. The whole thing finally got sorted out after a few phone calls and faxes (yes, I had my original receipt), and wouldn't you know, after all that hassle, I never needed the AppleCare for a blessed thing. That computer always worked well and still does, though it looks weary and worn now.
Anyway, the hint you might take from this story is to make darn sure you're reading your computer's serial number correctly when you talk to the AppleCare people again, and if there's a character in it that you could easily have misread or mistyped when you registered it, ask whether your serial number shows up with warranty coverage if you substitute the likely alternate reading of that character. You can actually check alternate serial numbers for warranty coverage yourself, using this page:
https://selfsolve.apple.com/GetWarranty.do
