Same problem here, headset detected as plugged. So i insert a toothpick into the headset connector, move it arround very carefully and start working.
I got the same problem with my nokia lumia 800 BUT the phone is a survivor and will heal itself... If it doesnt i'll probably send it to nokia care.
I had problem with my Lumia 800 where I had no audio sound on any calls - i.e.. I couldn't hear anyone. I installed the Diagnostic App by entering ##634# and ran that through...it didn't identify any problems. I then went through each category individually and eventually ended up in 'Audio Loopback' where I set the Loopback to 'Earpiece'. I then gained control over the audio up/down switch on the side and managed to get my audio sound up to 10...it had been on 0 (?) Whereupon....hurrah...hurrah...hurrah...i got the audio back on my incoming calls.
Hope this helps!
I ran the diagnostic code over my lumia 800 and with the audio test the problem was solve... I can ear my call phones again without de headphones. But I'm affraid with that problem... It seems that the problem can easily back again I hope that doesn't happen.
i joined this forum to check out my phones no sound problem.Tried cleaning jack socket with paperclip and now phone working again,cheers for the advice.
I have tried all this and reached the same conclusion. Do you think there is a way of tricking it into thinking that the headphone is disconnected? Maybe there is a nokia equivalent of the iPhone jailbreak which can help achieve this?