I did the power OFF steps, BUT...my cable provider has combined the modem and router into one box, which I must reboot as a unit, and I have no control over its turn-on or turn-off sequence. Also, I won't be able to say whether this helped until I operate my browser for a while to see if the fake popup occurs again...or not.

I started FRST as Administrator and clicked Fix. FRST then gave a popup saying it cannot find Fixlist. Do I need to do something to/with the text you instructed me to highlight?