Does anyone else have trouble with the chest strap losing contact while biking? I have a Timex one, which is great for skiing and running (I chose it because you can change the batteries yourself, and it had features that would have cost an arm and a leg on a Polar), but it seems to not like the biking body position, or something. I quit using it biking, because it would just drop to 30bpm, or it would jump to 300 (probably picking up the signal from my computer), or lose the signal completely. I'm assuming it gaps in front sometimes, due to body position, and loses body contact.