why doesn't my headphone jack go in all the way?

I have recently got a macbook late 2008 unibody which im completely over the moon with, but I have one problem. when i got to plug my headphones in about 1 or 2mm sticks out of the jack, this makes it really hard to listen to music as it really tempermental and has to be kept in the same postion, does anyone know why this is? I have tried with my solo HDs and JVC gummys and it still sticks out, anyone got any ideas? thanks