Comment 46 for bug 565685

Under Fedora 14 which I realise may not be called for here, I have the same problem, however, after removing PulseAudio, and using alsamixer under terminal, the problem is non existent.

Under alsamixer:

Headphones - No effect on either headphone jack or internal speakers
Front - Seems to control the sound coming out of both outputs, however, stays muted or sound will come out of both outputs

Independent is Off - If on, no sound comes out of the headphone jack.

Hope it helps someone.