eMacMan

MY OS is anything but up to date. So this may be another false lead.

You could try Onyx. That should allow you to disable Spotlight or at the very least rebuild the index. It is not as intuitive as Spotless hence my original recommendation.

I recommended disabling Spotlight as a test. That's because an index rebuild takes a loooong time and the computer is best left to its own devices while that is being done.

I do hope that is the issue, as everything else I can think of is likely to be more expensive or require more effort to solve.

You kindly recommended Spotless for turning off Spotlight. However downloading its most recent version (2 years old) doesn't boot on this Mavericks Mac. Know any alternatives?

Fixamac's website lists all versions as targeted to specific OS's, the most recent being Lion.