The other night I bought the car dock, and a cassette tape thing so I could listen to slacker radio and do hands free calls in my truck. While everything is hooked up, it works perfect. I can hear slacker and calls just fine though my speakers, and callers can hear my voice just fine. The problem comes afterwords. When I unhook everything and exit my vehicle, if I get a call (the ringtone does come on) I cannot hear callers through the normal speaker. If I put the phone on speaker phone, I can hear them just fine...but if I take it back off I can no longer hear them. A simple power off/power on seems to make it go back to normal, but is there anything that causes this? Is my unit defective?