Sound comes out of only one headphone

Could be a broken wire or faulty plug/socket. Try another pair and if the problem is the same with those, the fault lies with the equipment you are plugged into. If the faulty headphones work fine in another piece of equipment then again the original equipment has a fault. If the original headphones have the same fault in another piece of equipment, then they are faulty. It is all about elimination. Once you find the faulty piece (headphones or equipment), then you can start to try and trace the cause.

Try another set of headphones in the device you are having a problem with. This will eliminate the device being faulty if another set of phones work with it.
Check the jack plug on the "non-working" phones is the same size and design (count the rings) as the working pair.
Try the "non-working" in a different device.

Is the sound on both channels on a pair of headphones? If it is suspect a faulty headphone socket, especially if the speakers are cut out when the headphone jack is inserted - normally.

The cable that is used in the headphones is actually very low quality and very weak so easily broken, You may be able to remove the wiring from another pair of headphones and use it.
Unfortunately Skullcandy are not a high end brand so no spare parts are really available as they are made in china as you can see on the following link.
Link:

The headphone socket in the GoGear is faulty. If you can hear sounds from both ear pieces when you wriggle the headphone plug in the GoGear, then the headphone socket in the GoGear is faulty. This fault can be easily fixed by removing the circuit board in the GoGear and resoldering the headphone socket to the circuit. You need a very fine tipped temperature soldering iron to do this job.

i had the exact same problem but i just removed the smallest extension cord its like only a few centimeters :P after that the sound got clear without having 2 use the button

If possible try with another pair of headphones. If speaker outputs are ok, probably indicates a faulty output of headphone amp, if is seperate circuitry from speaker output.

Broken audio cable entering the transmitter or audio jack plug.

Power supply plug loose / faulty power supply.

the pop port on your phone may be dirty or broken

The same happened to me. JBL says that repair services are not available for this product according to their website. Their suggestion is to buy a new pair!!!!!. What a shame. JBL products are quite good but the post service is ****.