I have the same problem in the Mac Calculator program. It turned on somehow, and I can't turn it off.
The above prescption doesn't work. It keeps right on announcing the keystrokes.
I hve tried to undo every setting I can find in Preferences, but nothing works. Keystrokes won't turn it off and Text to Speech check boxes won't turn it off.
This is really annoying to me and the people around me.