Well... Thought I'd post an update here in case others run across the same problem.
I just couldn't get the Mbox2 mini to work on my Sonar X2a system, so I bought a Focusrite Scarlett 2i2. Boom...everything works great in Sonar.
Now I'm trying to get it to work with Pro Tools 9HD. So far not able to. Focusrite says it will work with PT9.

I know this is a bit late. I recently acquired and Mbox 2 Mini. Playhead would stick. I disabled the "UserHardwareSamplePosition" in the configuration file in the Audio section of Preferences. Work like a charm now.