Hi Steve,
just an update. Last night, I was listening and editing and I experience another computer shutdown. Restart and recovery was without incident, but again, I noticed that when I opened MusicBee after the shutdown, the residual music in the playlist and some other screen information was from a status earlier than when the shutdown occurred. This reversion to an earlier status has always accompanied these shutdown events.
In addition to using MusicBee, I also use the MusiChi suite of player and editor programs. In fact, I used MusiChi to completely rip and store all of the files from my CD collection (over 23,000 files). So, I have a great deal of experience with MusiChi. Using MusiChi has not been without incident, but I have never experienced the unexpected and complete computer shutdowns which have occurred when using MusicBee. Therefore, I do not suspect hardware issues as the cause.
The interesting aspect to these shutdowns is that, when it happens, it is instantaneous. The sound stops and the computer is instantly and completely turned off. If this problem is unique to me, then there is no point in worrying about it. If you receive other complaints about instant computer shutdowns, I'll be glad to gather data of whatever kind might be beneficial to help solve the problem.
Best,
Art