My Nike chip for Ipod is crazy!

I have a Nike chip for the Ipod and I loved it until it started to do whatever it wanted to. When I go for a run it seems to tell me a different distance every time. Now I know that it calculates the distance based on my stride so I do not expect it to be perfect but I know my stride is not changing that much and the inaccuracy is sometimes a difference of 3 blocks. This is just crazy!!

I have tried calibrating it over and over again, and nothing one week it tells me to turn around at 30th the next week it tells me to turn around at 33rd I don't know what to do!? So I guess I will just turn around somewhere in between?! Does anyone else have this problem?