I have an iPod Touch 2G running firmware 3.0. Today I bought some new nike+ shoes and a sensor. I got home and put the sensor in the left shoe, enabled Nike+ on the iPod, and pressed the sensor button in the menu. A voice said "Walk around to activate the sensor". So I walked around, but the sensor was not found. I've tried holding the little button on the sensor for three seconds several times, still the sensor won't be activated or detected. What can I do to fix this? Have I done something wrong?