ZC Custom Quest Background Music Gone

Was playing a quest on ZC 2.50 RC4 without problems this morning. When starting up the game later in the day, there is NO background music at all. Sound effects still work oddly enough (swinging sword, rupee, killing enemy, etc). Appears to be no background music with other custom quests as well. Not sure if it's a program issue or a driver missing or something else. Didn't change or install anything new during the day. Wondering if my computer somehow isn't picking up MIDI files.

What can I do/change to get the background music to work again.

Thanks.