Static When Recording in Garageband 3 HELP!!!

Hopefully someone can help me. I am using a M-Audio USB box that allows me to plug my microphone using an XLR cable into the M-Audio and then into the Powerbook G4 with a USB cable. When ever I record vocals there is a crackling over the sound. The strange part is that it does not occur when I tried recording into Sound Studio with the same set up. I have tried restarting Garageband several times but no help.
I have tried having both the Audio input and Output both set to use the M-Audio and still the crackling static.
It does not happen when I use the internal microphone in the powerbook. Does anyone have any guesses.
Oh I also tried it with the computer being plugged in and using battery power. THat didn't help either.

Help!!!