Headphones not working on macbook but they work on ipod and iphone

Sound will come out of the speakers of my macbook, but the headphones do nothing. This just started, so I tried a different pair of headphones and it worked fine, but I unplugged the new pair just once and they stopped working when I plugged them back in. They still work on my ipod and iphone though. I'm guessing the first pair still work on ipods, too.
What's going on?

First guess would be a damaged headphone jack port that gives you an intermittent connection.