Thank you so much, Thomas, Andrew, and "v", for replying to my post!
And it seems that the hunch you all had was in fact correct, as it
turns out: so I had my hubby remove the light fixture, and alas we
found that the bulb was indeed one of those compact fluorescent
energy-saving doohickeys- "batta-bing, batta-boom." (I guess it was
so many years ago that we put it in, that I had forgotten what type of
bulb was in there!) Well thanks again- that's a big relief to know
that it isn't some more serious problem, and this saved me from having
to call the electrician. Happy New Year.