Playing around with Find My Mac, now can't unlock!

I have had an iCloud account for awhile and have a few devices on it. I just bought a used white MacBook (macbook7,1) on Craigslist a few days ago and was just playing around with iCloud and locked it with Find My Mac. I swear the web interface gave me eight boxes for an eight digit passcode, but now the MacBook is only giving me six boxes so I can't completely type out the passcode I entered.

I can't get this thing unlocked no matter what I try! I've tried various combinations of moving up and down the number row (I used the same passcode I use for everything) and still no luck. Ahhh what can I do!?!? I put in a Lion DVD and it still boots up to the passcode screen.

Here's a screenshot of the email I received from iCloud on my Mac Pro:

Well, I took took it to the Apple Genius Bar today, and after demonstrating it was indeed locked via my iCloud account by signing in and locating it at the Apple Store and sending it a message, the Genius kindly took it to the back, and returned with it working. He said he removed one of the memory sticks so that the memory configuration would change, thus resetting the firmware password, and then zapped the PRAM three times in a row. Works perfectly now and wasn't even charged for the service!

Hope that helps anyone else that runs into this in the future.