I did some searching in the Apple support forums and didn't find much. The one person I found having a similar problem (albeit with a different version of OSX) doesn't seem to have found a solution.

I've been using a USB DAC (nuForce Icon uDAC-2) with my OSX machines for ~18 months, and with my retina Macbook Pro running OSX 10.8 since August. In the last few weeks it's started to have problems. The audio will drop out about 40 seconds into use, and it doesn't come back until I disconnect...