iPad 2 thinks it's plugged into dock

I noticed my iPad 2 16GB Wi-Fi had no sound, but all the sound settings and lock switch are set correctly. Then I opened the iPod app, it showed "Dock Connector" in the top-left where the volume control normally is. But my iPad was not plugged into a dock.So I plugged it into my car dock. It plays music/sounds. When I unplug it, I get volume control back. However, if I sync it or plug it into the