just had the same problem RIGHT NOW - i took an air duster can (those pressurized cans that are made for dusting computer components) and i blasted the headphone jack....worked like a charm...i guess there was some dust or debris in there that got in the way and confused the computer's jack....i would suggest trying THIS method before sticking anything INTO the jack or blowing with your mouth (in fact, with all due respect, DON'T blow with your mouth...saliva will get in and RUIN the jack and sticking a screwdriver into the jack will only work against you, imho) all the best!