As far as I can figure out, it all began after I installed the latest version of Flash 10. The error message pops up when I view Flash movies in Internet Explorer, Opera or Firefox. When I Googled for information, most of the hits referred to problems with something called the Google Desktop rather than Adobe Flash.
I didn’t think I had the Google Desktop installed. But when I checked via Control Panel, there it was. I must have installed it ages ago in a moment of recklessness and have never used it ever since. I couldn’t see what on earth it had to do with the Flash movie problem but, just on the off-chance, I uninstalled it anyway.
And, much to my surprise, that did the trick. Getting rid of the Google Desktop has had the effect of letting me view Flash movies without any errors.