It's the 'Song Title' field. I actually just reporduced this again, causing Windows Media Player to lock up. If I blank out the 'Song Title' field, and create a MIDI, the MIDI will crash PTP w/an 'Error: 230' and lock up Windows Media Player if I try to play the MIDI file in those programs. I don't know about RealBand since I don't use it. BTW I'm running BIAB 2009 on Windows Home Vista. Solution is simply to never leave 'Song Title' blank. Very obscure bug none the less.