Blue Nessie vocals

I'm a new Garage Band user and I'm having trouble recording vocal tracks. I recorded my guitar part (real instrument) no problem and it plays back fine. However, when I try to record a vocal track via my Blue Nessie mic the track is filled with feedback/static. The vocals are there, so it's recording, but static fills the track and this seems to occur no matter how I tweak the settings. Any suggestions?