GF - had something like this tho' not as nuisansical. BOAC Captain's story also sounds faintly familiar. Also problems with McAfee's "Scan on Demand" not working properly. Also annoying non-fatal exceptions.
Cured by uninstalling and reinstalling McAfee. If you don't get a clean ininstall (I seemed to but did a [tedious] manual check anyway) you may have to do a manual uninstall.
Instructions (complicated) for doing a manual uninstall of McAfee emailed to you directly. I had quite a time prying this out of McAfee and it is not for the fainthearted.