Audio Issue with my MacBook?

Up until 2 weeks ago my Turtle Beach headset worked fine with my MacBook (Mid 2007) but since then, the audio has been alternating between the left and right sides.

I have checked and the headset is not only compatible with my Mac, but it isn't the headset that's having the issue.

I can take this headset, plug it into the Macbook and it will have the issue.

If I plug it into my Windows Desktop it doesn't have the issue. I assume that means the issue lies within my Macbook, but I haven't changed/downloaded anything that would affect this. I have taken great care of the macbook and haven't been rough with it (purchased it secondhand in August) but it has had no issues since.

This is just really annoying because I use Skype, and use many things that require me to use headphones to listen to music/people/movies but am now unable to due to this horrible issue.