I was having all the problems everyone has talked about above. Volume bar would show up intermittently, I would have to unplug then plug my earphones back in to get it back so I could listen through the ear plugs. I could charge it on my dock but can't play music on it through the dock.
A friend had accidently spilled red wine on my phone the night before I was to fly out of the country for a couple of weeks, it had a pretty good case on it, and everything seemed to be working so I didn't worry about it. Then it started showing the warning that its connected with something not compatable, even though nothing was plugged in.
My fiance pulled the phone apart, gave it a good clean out (as people here had suggested). It didn't help. He then pulled it further apart and saw that there were some plugs in the dock connecter that were burnt. He said it would have been caused by the wine, the dock connected part getting wet, and shorting out.
So I have ordered a new dock connector assembly part, he is fairly certain that will fix. Will update when we get it (hopefully in a few days)