I have read that others have had problems with using the M-Box soundcards, but thought I would post my experience here also...
I can get 0.41.4 to work with the M-Box Micro, however on exit I will get an OS X crash message, even though the App appears to have closed completely - there are no open windows and no icon in the Dock. After the initial crash, I will get more random crashes - often on opening Pd, and without fail when trying to change Audio Output back to inbuilt soundcard.
System:
MacBook Pro 2.6 GHz Intel Core 2 Duo
4 GB 667 MHz DDR2 SDRAM
OS X 10.5.7
M-Box Micro
Anonymous
There have been lots of updates to the audio handling, is this still a problem with 0.43.1? You can get a beta build here:
http://puredata.info/downloads/pd-extended/releases/0.43.1/