I get random static problems with GarageBand?

I record Let's Plays for YouTube, and I'm a mac user, so I use GarageBand for the commentary (live commentary by the way). Each video is about 15 minutes long. So randomly, maybe every four episodes, a whole minute of the commentary becomes really staticy and I have to mute that part. It's not only staticy, but it like.... echos, if that means anything to anybody. I use the automatic level control also when recording. So far, its just been REALLY annoying, but I'm worried it could get worse. HELP!!!!!!!!!!!