iTunes Songs Only Playing Out of One Headphone

I’ve been using the Sansa Clip for years. Until now, I haven’t had a problem.

When I dowloaded a number of songs from iTunes and put them on my mp3 players, however, the audio would only play out of my right headphone. I noticed that the songs were downloaded in mp4 format, so I converted them to mp3 format and re-synced them. I still had the same problem.

Is there a reason why the audio is only coming out of the right speaker? I don’t think it has to do with the audio jack, since I haven’t had a problem until I tried to use songs downloaded from iTunes.

Are the downloads not in the right format? Is there a way to fix this without having to simply give up on all the songs I bought?