I've done this several times, and it sends the patch I choose correctly, but as soon as I play the song the patch changes to a patch number unrelated to the number I chose, and to general MIDI, for that matter.

For example, I chose the K2000 patch #2--Stereo Grand, and saw the K2 screen for that channel go to that patch. As soon as I hit the play button, it changed to patch 91.
Can anyone explain what's going on and how to fix it?