OK... I think that I've finally rooted out the problem with the cable modem that has plagued me for weeks. We will have replaced every piece of coax and every splitter between the wall and the cable modem, but what the heck. The intermittent problem has been highly frustrating.
So... with luck I will be more consistent in my time online and on-grid. Whew.
UPDATE: I spoke too soon; the connection is still flaking out. Someone's coming in to look at it... again... today.
UPDATE: I have my fingers crossed (which makes typing difficult...). The fellow came back, and I have to admire his doing so that late in the nasty weather we're having, found a problem outside, and fixed it. So far, so good.