My audio socket in my iPod Touch started broadcasting both channels in both earphones. I deemed the socket to be faulty.
While I was reading the instructions on how to reassemble the device (better know how to glue it back together before I tear it apart, I thought), I read an interesting user comment attached to the introduction:
"BEFORE TO OPERATE, make sure that your headphone jack problem is not a clump of pocket dust stuck into it."
I decided it might be prudent to follow this advice, and went digging around with a needle in the audio jack. Sure enough, out came several small clumps of pocket lint, and lo and behold, my audio socket was good as new.
Always eliminate the simple possible causes for issues before you go spending over $50 on parts that you then don't need. I feel rather foolish.