This may be more revealing. An email to Andrew.

Hey Andrew,

OK
You couldn't reproduce it the other day. Today I thought I'd load one of the mgu files that I originally used and see what I could do. I left all of the Blue Tracks alone and just muted them. I kept adding RTs one at a time. I saved the song and restarted the program each time I added a track. I would then load a different song and play a few bars. I then would load my test song, confirm proper play, add another track, save, restart and so on. I was able to load all 48 tracks!!! and it played perfectly. Only the first 5 tracks were muted MIDI.
I then deleted the BLUE tracks saved as test2 and restarted the computer. All remaining 43 audio tracks played perfectly.
At this point I figured I couldn't reproduce it either. All 150 songs were done with v3 before the last BETA.
I shut down the computer to go to lunch. When I got back I thought I'd test some more. I opened my test song hit play and everything locked up.I had to remove all but 5 tracks to get acceptable playback.
Why would restarting the computer affect the file playback. turning the program off and on didn't. Doesn't make sense to me.

John
ESI Gigaport HD+
Lenovo Turion II /4 Gig Ram/ Win7x64 be
15.6" Monitor
"The only Band is a Real Band"
www.wintertexaninfo.com/BANDS/JohnnyD.php