Figured it out. My cat somehow enabled some functions in Universal Access (which I've never had reason to use before, so didn't recognize). Maybe she's trying to tell me something. All in all, it beats the time she sent an email.
So, what keyboard combination did my cat inadvertently press so that I'm now seeing a black frame surrounding active areas in whatever window I'm working in. Including the text entry box that I'm typing this into? Also, various menu items are duplicated. Such as Restart Restart, Shut Down Shut Down, Log Out Log Out, etc. Where did this suddenly come from and how do I get rid of it? Tried restart. 10.5.8. Thanks.