Ipod Nano (7th gen) and nike+ stops during workout

Hi there,

I used my Nike+ shoe sensor along with my iPhone 4s for a while. All worked great.

I bought a new compatible Polar hearthbeat sensor and a new IPod nano 7th gen.

All ready to go I thougt.

The iPod Nano recognises both the sensor and the polar band. I can start a basic run with a playlist.

After about 2 minutes the iPod stops recording movement and hearthbeat. The music and time elapsed continues however
after syncing to Nike+ the activity/hearthbeat line goes to 0.

If I use the same shoe sensor with my iPhone 4s it all works great. However the polar band
isn't compatible with the iPhone 4s.

Any ideas ? I already updated all the software to the latest version.

Kind regards,

Walt