[Brian]

I was able to change my shortcut from command-F6 to command-F5 and back again without un-checking that box in system prefs. Also discovered that the "activate Voice Over" service is enabled by default and set to command-F5 in the process. Gave myself a bit of a scare with that one. :-)

I do suspect that something is up here on the OS X side of things, but have never been able to nail down what's going on. Any help in doing so is greatly appreciated. :-)