Yeah, I have that problem w/ my headphones where after a certain amount of time, I'll have to mess w/ the wiring near where it goes into the headphones so I can hear from the left side. You'll have to replace them.
For my headphones, I have a lifetime warrenty
on my PortaPro headphones from Koss, so everytime my headphones start to short out, I just pay $10 to ship it to them & back & they send me a brand new pair. Beats having to spend $50 each time.