Had the same issue after update, as well as a 'ping' sound at start up. Reset didn't help. Reinstall via NSU didn't help either. Sent it to Nokia Care 2 Fridays ago, and they're replacing the motherboard. Stil haven't got it back though, so couldn't say if the problem is solved. Off topic, Nokia Care is REALLY sucky after Nokia sub contracted it to some jokers. Before it was on the spot repairs or 3 days at most. On the plus side, I gained the breathing LED notification light at the expense of the headphones...
My N9 still detects my headphones normally in PR1.1. Try a hard rest and see if it cures the problem.
I also have problem, but with not nokia branded headphones..