Nokia Nseries :: 5530 Constantly Asking To Select Accessory?

Have had this phone for a couple of years - i haven't done anything recently that i think may cause this problem.Today a message comes up every few seconds asking me to select an accessory (headset/headphones/lineout/music stand) - it thinks i have something plugged into the audio socket. I do not! I have not used the audio jack for at least a year!I have rebooted it & taken the battery out. I've also reset to factory settings & reinstalled the software, but still i have this problem.In this state, the phone is not usable since this message constantly gets in the way.Earlier on today the problem was different, a symbol came up at top right meant a headset was connected (when the truth is it wasn't). This meant i couldn't use the phone to call people as we couldn't hear each other. After this, i changed some bits in the accessory settings & now i have the problem i described at the start of this message.