This is not a question - Rather a solution - I have just confirmed, something that I believed to be true for over 3 years.
The MOTU drivers for the PC are not as good as the drivers for the Mac. I have just recently purchased a Mac (like 5 days ago) and after setting it up, a problem that had existed for years on my PC-based system, instantly vanished.
The software/hardware environment: Studio One 1 Artist, Studio One 2 Professional, Studio One 3 Professional, MOTU MIDI Express XT, StudioLive 16.4.2, Alesis QS8, EMU Proteus /1 Orchestral sound module.
The Problem: I was attempting to play an external sound module via my MIDI controller, through Studio One, running on a PC. Intermittently, it would work (like 60% of the time). I never found a duplicatable procedure to make it work.
The solution: I purchased a Mac, immediately downloaded Studio One 3 Professional, setup all my MIDI devices in AMS MIDI Studio, and then launch Studio One. The problem was instantly gone.
Presumably the problem always has been the MOTU Drivers.
PC Users beware.