Got the button press debounce fix working. (current MPGuino code version is at first post of this thread)
Debounce timing adjustments may be made by adjusting the following two lines in the code.
Code:
const unsigned int keyDelay = (unsigned int)(t2CyclesPerSecond / 256ul);
const unsigned int keyShortDelay = keyDelay - (5 * keyDelay / 100); // wait 5/100 of a second before accepting button presses