I’m having a similar problem, except that I’ve already read/done everything on this forum (I think)
I have a new Mac Air v 10.8.6, using a Fast Track usb w mic. According to the fast track, the mic is picking up sound. My computer recognizes the fast track and I’m able to select it in all relevant input/output fields. The fast track works just fine w my friend’s computer, but refuses to record on mine. I have the most recent drivers from avid’s website. I’m also unable to record in Garage Band and I’m at my wits’ end! Switching mikes does not help. I’ve restarted multiple times. I have all of the settings you’ve described above.