I recently installed a MXO2 Mini with Avid MC 5.5.3, and I have everything running smoothly, except for the audio scrubbing. MXO2 Mini hooked up through HDMI to HDTV + built in speakers.
Mac OS X 10.6.8
Matrox Driver 2.5.0.0034
Initially the digital audio scrubbing was only outputting sound every 6 - 7 frames, and all the voices sounded very stuttery, not smooth sounding like usual digital audio scrubs.
After disabling Fast Scrub in the timeline options, I was able to get the digital audio scrubbing to work a bit better, but when holding down the advance 1 frame key to play the audio in realtime, the audio still only plays in 1 frame bursts when Caps Lock is on... Same stuttering breaking actor`s voices.
Making JKL the only way to "scrub" through audio and be useful.
I also tried MC 5.5.3, and the Matrox 2.5.0.0034 driver on a Mac OS X 10.7.3 install on a separate drive, to make sure it wasn`t Snow Leopard causing it, but the same issue is still holding there.