Fluttering noise while playing through iTrack Solo.

I recently bought an iTrack Solo to use with a Macbook Air and Garageband, however there is a loud fluttering noise whenever a note is played through to the Garageband interface. I've tested multiple cables, reinstalled the drivers many times, and tweaked the I/O settings on the Macbook and Garageband to no avail. I just tested the iTrack Solo on a PC with Guitar Rig, and it works like a dream, so I'm left feeling like there's something wrong within my Macbook. Does anyone have any ideas?