I'm developing an editor for the MU128 and a download is available from www.robotsoftware.co.uk/comingsoon.htm.
Its still in development so this message is to get some feedback and some beta-testing. Its still usable at the moment. Some features are disabled and only works for 16 parts at present. Should be complete in a few months.
It uses Midishare as a driver so you may want to check out the www.grame.fr/midishare
if you experience midi problems and conflicts.