Headphones only work if already plugged in when the Mac is turned on

Question

I have a 13” mid-2012 MacBook Air running Mountain Lion. I recently noticed this problem with headphones. If I plug them in when the laptop is already running, they don’t work at all. Sound continues to play through the speakers, and the OS doesn’t recognize that headphones were plugged in. If I go to Sound on the System Preferences, the headphones don’t show up at all on the list of output devices; only the integrated speakers show up. If I alt-click on the sound icon on the top bar, there are no headphones listed under output devices either. The sound continues to play normally through the speakers as if the headphones weren’t plugged in. However, if I plug in the headphones when the machine is turned off, and then turn it on, they work perfectly (well, sound quality isn’t great, but they work). If I then unplug the headphones and plug them back in, they don’t work anymore as described above. I tested this with multiple headphones, all of which work normally on other devices like my PC, iPod and Android phone. I tried resetting PRAM and that other thing (SNC?), didn’t work either. I don’t think it’s a hardware problem, since it works normally under specific conditions. Sounds more like a software bug, but I’m no expert.. I searched around for issues like this, but only found generic answers which didn’t solve the problem, as well as unanswered posts

Answer 1

Since this is a consistant  and repeatable issue, take it in to your nearest Apple store genius bar for evaluation.  If you are still under warranty, they should fix the problem.
Ciao.