I appreciate everyone's great advice.

Irulan, you're right, I was shifting under under load, so I probably did something because now those gears continue to sound crunchy as I pedal no matter what.

TigerMom, I think a chain catcher is a good idea. It's not too expensive and could help.

And of course, like everyone said, classes! I admit, I felt a little discouraged. I'm no spring chicken any more and I was wondering if I was just too old to learn.