Ethernet port problem

My ethernet port on my MB is fickle. The cord needs to be in there just right for my modem's internet line to be on. Sometimes if I move the MB even a little, the ethernet cable will shift, thus disconnecting me from the internet. When I jiggle the cord, it eventually reconnects. It's doable, but its an annoying problem that I think needs to be solved. Does anyone know what I can do? What sort of problem do I have?

Alright,
Have you tried more than one cable? If you have, get you a little flashlight and look inside to see if either of the little connectors has been been or shifted?

There's ONE cable that I have that seems to work okay. But it's still a problem for me because I travel a lot with my MB and can't use that cable everywhere I go. I don't think any of the prongs are broken. Any other suggestions?

Have you tried reversing the ends of the cables?