Hi JJVW
I found your post, and though its a few years old now, i'm hoping you still use this forum and check your messages.... I am in the same position as you were when you posted this-except that my bike has been sitting, locked, frozen and sad.
I just received my 2 replacement keys for my U Lock in the mail on Friday, and I tried getting my bike out to head to work today, and found that they fit...but dont unlock the lock. I know I'll come up against the 'our system is perfect, you must have sent the wrong serial number' argument, but I'm certain it was the right number, and I think the odds of having made an error in the digit which would have created an alternate combination for a different lock, are in my favor.
Anyway, i'm hoping you can tell me the rest of your story, and give me some tips if you have any