iPod Nike + Serial # Differences?

I just got my Nike + two days ago, I as very excited. I bought it from someone on the forum. He said he got it from apple and never used it.

I used it yesterday and it worked alright besides it not being calibrated and it horribly underestimating my distance. Today my ipod crashed and froze up, I had to reset it. I looked at the serial # on the nike + things. Strange, the little thing you put in your shoe had a different serial than the receiver (receiver has same serial as appears on the box) that plugs into the ipod. I know the receiver is supposed to work with multiple transceivers, so this shouldn't cause the problem I am having, but it seems strange to me. The serial # on the box and receiver shows up on apple, but the one on the transceiver is rejected by apple.
Are these #'s supposed to mach up?

Last two workouts it has worked fine, that one workout must've been a fluke.
Still I wonder about the serial #'s though.

It had been working fine up until today. I was 5 minutes from finishing my workout, and my ipod crashed/froze again. Does anyone else experience this type of trouble? I am trying to figure out if my ipod is crappy, or if the nike + has a problem.

I have a used nano 1st gen, latest firmware.