Hello.
Im one of those people that uses a headphones always on pc, but Im having a problem since a week now:
The problem is that while im using them (almost all time playing, watching videos or talking on skype) the sound starts playing through notebook speakers and headphones at the same time, like when you do false contact with them.
I think that happens when i move the notebook (I use the notebook on a little table on my legs, so if i move, the notebook moves too). To solve the problem temporarily i have to touch, turn or just pull a little the 3.5mm plug of the headphones, but just enough to move the notebook or the plug and it starts to happen the same again.
I think this info may help:
Thanks for any further help ;)