I resumed the FileMaker development session that was underway when I wrote my previous note last night. I soon discovered that the scroll button in my Mighty Mouse had stopped working in long FileMaker list (e.g., list of script steps). Since scrolling was working fine in other apps, I quit FileMaker and relaunched.
Two things are now working correctly in FileMaker editing:
1. Mighty Mouse scrolling
2. Command-C in a Specify Calculation window
In addition to Command-C working when the window first opens, the menu bar's list of menus is no longer changing when I press the first Command-C.
I'll be watching to see what triggers the erroneous Command-C behavior.