edit: i've found a way to "force" this event to occur: if i search a text file (i was searching the logs) for a word that isn't there, when the windows box pops up telling me it can't find the word, JRiver stops playback identically to the "random" occurrences.....i'm starting to see a pattern in the random but don't know how to read the logs
This is actually surprisingly helpful.
What happens when you do this is your soundcard makes the standard error "ding". That's causing the driver to lock up when it happens at the same time that MC is using the sound card. Assuming you have
WASAPI Exclusive Access enabled, the sound should just be "blocked" from happening. Instead, what is happening is that your sound card's driver is locking up and going sideways. In other words, it is not handling Exclusive mode properly.
That issue, as described generally, is almost certainly a problem in the sound card's driver. It is possible it is coincidence that it "just started" with a certain build of MC. My guess, in fact, is that a Windows Update (we've had a bunch of MAJOR ones recently) broke something in your old sound card driver. You correlated it with installing a new version of MC, but that was only coincidental.
Easy enough to test. Download and install an old version of MC. If you can roll back to a previous version of MC and the issue (now that you have a way to "force" it to happen) vanishes? Then it is probably something specific to the new version of MC (either it has a bug, or your driver has a bug that was previously masked by something in MC). If you go back to a version of MC20 from two or three weeks ago before the issue occurred and it does not change anything? Well then, it isn't MC that changed, it is something else on your computer.
If that is the case, then look to your hardware maker for a new driver.
It is worth mentioning that it could, also conceivably be, that your sound card is physically dying. This is probably unlikely, but it is possible. Hardware does not last forever.