FWIW, I've been having dropouts since Day 1 of running Mountain Lion (see here:
http://www.tonymacx86.com/audio/74916-ga-b75m-d3p-audio-skipping.html)
Yes, I know. Not the same board. Not even the same audio chip. I've just been dealing with it (tried every possible Audio MIDI combo)... even tried front vs. rear green jack. Supplemental 10.8.2 update came out... nothing. Updated Multibeast. Still dropping out. (didn't retest front/rear after those last two tho).
Decided to fiddle with it more tonight. Saw a BIOS update came out. Updated. Still dropping out. Saw this thread by chance and decided to try the front green jack again. What the hell... no drop outs for the first time ever. Had to have been the supp update to 10.8.2, newest Multibeast
(more likely), or going from F5 to F6 BIOS.
It's a little goofy plugging my speakers into the front, but I'm unbelievably happy now (ironed out every last gremlin out of my mt. lion hackintosh with this). Just thought I'd offer this as a data point.