I installed Build 22631.2338 yesterday, and have been playing iTunes with only one observable issue for 96 minutes. (Recall when I was having trouble, I'd start having display issues at around the 25 minute mark, and complete system failure at 45).
The only issue - and it could be totally unrelated - while working in another program (either Outlook or Word), a black rectangle flashed across the top of the screen. Just once. Weird, but I can live with this.
Thanks everyone for your help. We'll just presume Windows put some epoxy over whatever was leaking, and get on with our days.
So much time wasted, though! (On this, and on trying to get MusicBee set up as a good alternative; at best, I'd give it a B-).
Thank you