Problem with sound input

Hey everyone this is my first post here and i'm glad to say it's about a problem that I have! I've been using my macbook pro for recording, I would use a 1/4 and 1/8 inch converter to plug my guitar straight into the comp. It stopped working recently...in GarageBand, it seems like the input volume is maxing out (pic). At first I thought it was an issue with the converter, but the problem occurs regardless of if it's plugged in or not. Here's the pic so you can tell what I mean...

http://img13.imageshack.us/img13/6186/picture1kj6.jpg

Bump...was my question confusing?