First--yes, I can confirm that (a) both audio soundtracks are displayed in the timeline, and (b) I've tried loading other items that I knew had no problems playing in other applications.
However--Yaaaaaaayyyyyyy!!!!!!!!--it's fixed! When I had first installed 6.01 to try it out, I remember that just before closing it I had set VP's own volume control to zero, cuz I didn't want to annoy my wife who was also in the room watching TV. Then I closed the program, later uninstalled it, reinstalled 2.41, and found I had no volume in the old program. So, just now, on a whim, I reinstalled 6.01, made sure the volume level was turned up to full, THEN used Revo to uninstall 6.01 - and THIS time used the "Advanced" scan rather than just "Moderate" - THEN reinstalled 2.41, and everything's back to normal!!!
So, Revo really was the key, as it turns out. Thanks for suggesting it. The Advanced scan saved the day!!!!!!!