I just remembered this, and it partially does have to do with the wire. When plugging the wire into the headphones, make sure they are completely in, because they don't alway go all the way in. If not, one side stops working. That could be it.

I I don't know... I've had a pair of Beats Solo headphones for a while now, I think 3-4 months, and they work fine. It could be because yours were used. They were probably a fake pair, since those are floating all over the internet. If not, something might be wrong with the wires, or speakers.