The firmware update in MDM on Mac OS X now fails for me as well. Apparently one second after a MIDI USB device is connected, Mac OS X sends one MIDI message (don't know why it does it) to the MIDI device, the bootloader cannot recognise it and resets MegaDrum.
As a workaround I added a Mac OS X version of mdfwupdate utility in Updating firmware with protected bootloader. Please, note a step there which is marked in red - it's there to workaround this feature/bug in Mac OS X.