Instrument voice problem in MIDI after adding 11th instrument

Hi,

MuseScore Version: 0.96 r2674 beta 1, released 1st February 2010. I'm using Windows 7 32-bit. SountFont used is TimGM6mb.sf2 , the one recommended in the handbook.

I'm using MuseScore to make a MIDI from a song. Periodically, I save a MIDI copy and listen to it in Windows Media Player & RealPlayer to make sure I was doing right.

Everything was OK until I added the 11th instrument. It sounds fine when I play in MuseScore, but when I "Save a Copy", the resulting MIDI sounds wrong.

The first instrument in the score is "Nylon Guitar", while the 11th instrument is "Overdrive Guitar". The saved MIDI had the "Overdrive Guitar" voice where "Nylon Guitar" should be played; and when instrument #11 "Overdrive" is supposed to play (bars 38 - 45, 1:44 onwards) , it seemed to cancel out part of what the "Overdrive" in instrument track #1 played, so only 1 or 2 notes can be heard instead of the chords I've inserted.

No problems with the other instruments, though randomly but rarely, when saving a MIDI, the 1st instrument would be fine, but another instrument would mess up, eg. instrument #4 Music Box would play with some other voice that I can't identify.

I've attached 5 files:
The version with 10 instruments, playing correctly - the .mscz & the .mid .
The version with 11 instruments, playing incorrectly - the .mscz & the .mid .

And the last one is a version with 11 instruments, but curiously, playing correctly. I did not change anything in the score, IIRC it appeared when I repeatedly tried saving, closing, & restarting MuseScore, but subsequent attempts to get another correct one didn't work out.

I'm not sure if this is a bug, or I have made/changed a setting wrong, or if it's a limitation of MIDI. I'm new to MuseScore & MIDIs, I was testing out making a MIDI. Any support would be appreciated.

Thanks =)