Thanks so much for taking the time to try to help. I finally got it (more or less) sorted out with Support (the amazing Kent, who was extremely helpful and frank), and am posting the results here in case anyone else has similar problems.

1. Entering notes via both computer and external keyboards not working properly. I was running it off the external hard drive from PG, and did have it all set up properly, as Support confirmed. So he had me install it on my computer's hard drive, then copy it back to the external hard drive (being sure to take out the real drums and tracks folders first, then put them back afterwards), and that seemed to fix it. Some sort of corruption problem, I assume.

2. Editing notes spotty and problematic. Support confirmed that note editing is cranky. For example, you can't drag a note down into the space below the treble clef and above the bass clef, say to an A or B below middle-C. There are many other little quirks as well. So, it seems my editing is working about as well as it is going to, which is not very well at all. I hope PG pays some attention to cleaning that up in the next release.

So, that seems to be it for now.

Thanks to everyone who responded.

--Matt