I get a lot of questions about the MPD32 hookup to Reason. Thing is, all I did was plug mine in and started playing with it. I didn't make any settings. Is your MPD set to the Reason preset (#2)?
If that's all good, I suggest you try uninstalling/re-installing the MPD32 drivers on your computer. From the questions I'm getting, people are having problems because they use the MPD with another software besides Reason. If you're doing the same thing, it may be possible that the settings from the other program are conflicting in some way.
Grace and peace!