Plus dynamics are missing, and when I move the mouse around the screen, it inserts new stave lines.... not entire staves, just single lines.  If I continue moving my mouse around, the entire screen just fills up with lines.  I tried opening various files and it happens with all of them.

What is your OS?

Windows 7

After installing Finale 26, did you restart your computer?

I can't believe I didn't try that first. Sigh. Thank you.