Ipod/speaker dilemma

[Richiedoggs]

Hey everyone,
Over the weekend on our way to white castle, a friend sitting in the back noticed that only the left speaker was working when i was playing the ipod through the aux jack. I had the ipod wired from a cord with the identical plugs that go from the ipod's headphone jack directly into the aux jack. When the regular radio played, both rear speakers worked fine. Is something wrong? Is there a quick inexpensive easy solution or fix?