No sound on MIDI playback, but it's weird

Hi All, I just got X3, the basic version. I have used previous versions successfully. I'm trying to record MIDI data from a classical organ and then play it back. When I record, I see the captured data in the event list just fine. When I go to play it back, I also see MIDI activity on my MIDI interface, indicating data flow. This organ uses SYSEX messages to communicate stop changes (each "stop" being a sound on the organ). Interestingly, during playback, the SYSEX messages are doing their work because I see the organ's stops changing. However, the notes don't play, even though the MIDI lights on the interface are alive with activity. I went as far as to try to record from one computer to another to try to see if my captured data is transferring properly. However, it seems that nothing is being sent/captured, regardless of the indicators.
 
Any hints on what I've done wrong? There must be some setting I'm not seeing, or something.
 
Thanks,
Doug

Thanks for the suggestion. I changed the buffer size but it didn't seem to solve the problem. I began to wonder if the data being sent out was actually matching the data shown in the event list, so I set up a second computer with the software on it so I could capture and look at the data from the first computer. What I saw kind of stunned me: all of the data is registering as program changes rather than notes in the second computer's event list. How could this be? Thanks in advance for your help!
Doug