I had the same problem in Yosemite: Monkey would hang on launch, bouncing in dock, preventing me from updating HD500x or Variax. So frustrating...
FIX!!
\Library\Audio\Plug-Ins\HAL folder (off Root, not your personal library) may have audio drivers. In my case, it was the driver for the utility Hear, but it seems there are others which will also crash Monkey. Try removing any files in there, at least temporarily, then reboot. Fixed my issues... Of course, removing those drivers will cripple software associated with them, which is why you may wish to cut and paste them to somewhere else, then put them back, depending on your circumstances.