Hi guys-
I just ran Spybot S&D (thanks for that, musicman100! Malwarebytes wanted me to sign up for a "free" offer or purchase with PayPal, of all things!

). It identified a "DoubleClick" cookie which, depending on who you ask might or might not be awful. It looked awful enough to me, so I removed it.
It was identified as an Internet Explorer cookie, which is a little weird since I use FF, but maybe the browser doesn't matter. Anyway, it's gone.
I don't know how I'll know if that was the source of the problem, but I guess time will tell after I change my passwords (again).
@Russell: That's encouraging. I didn't see a phone# for them, but I was doing several things at once, so I'll check again.
Thanks, as always!
-Susan