Using MBox 2 With GarageBand on MacBook Pro Lion 10.7.3

Hi. This is my first Apple Support post. It was recommended that I post to this forum. I've been using my good old MBox 2 with GarageBand on my old MacBook without incident. Someone stole my laptop so I had to buy a new MacBook Pro the other day. On that system, GarageBand at first didn't recognize the MBox at all. A trip to the Genius Bar led to downloading a core audio driver. This enabled GarageBand to recognize the MBox 2 as an interface, and it records without much incident when the audio input/output settings remain on the DigiDesign MBox. HOWEVER, when I change the audio setting to the build-in output, all **** breaks loose. The selected signal bar starts registering a regular, loud, red-lining metalic beeping sound, and at this point the issue remains whether or not I change the audio setting back. They've tried several audio drivers at the Apple Store and nothing is working. Avid requires you to buy support codes, which is ridiculous, so any help on this forum would be extremely appreciated. Thank you!