AUX Jack balance problems...

[Parmalot]

So I've had my '09 Yaris 3dr liftback for about 2 weeks now. My gf got me a iPod Nano for Xmas and I was VERY excited bc my Yaris has the AUX jack, BUT...when I play my iPod through the AUX jack I only get sound out of the front left speaker. I messed with the balance and fader and I can get some sound out of the back left, but if I turn it to the right speakers no sound comes out (neither front right or back right). I had this SAME problem with my Corolla that I rented before I got my Yaris. I tried the cable (to make sure it was not the problem) in my mom's Sentra and it worked fine. Can somebody please tell me what could be wrong? Thanks guys. Cheers.