I did all the above methods,
and I still get the annoying message popping up on my iPhone 4.I`m not convinced it`s dirt or water on or in the connector part of the iPhone.
This only began to happen AFTER the initial contact with the Ipod docking station.
I also have an iPod touch 4 generation,
and after coming in contact with the docking station,
the same annoying message is being displayed.
The iPod docking station is brand new and clean.
I believe this is a re-programming issue between iPhone / iPod and docking stations in general.
I wish there was a definitive solution to this most annoying message!