I'm responding to my own post, yes, but, as it turns out... the cable modem isn't an issue - I tested out another cable modem I had handy with a very helpful Comcast tech on the line - forgot to take down his name, he deserves a cookie, or something.
Anywho, the upstream/downstream signals were outside normal parameters (especially upstream, though still not horribly off), but I've arranged for a tech to come out this weekend to again, diagnose the lines... and then refer to another tech who, apparently, would install some sort of device that boosts the upstream signal... I vaguely recall having had that done when I was living in Southborough. So, cable problem solved (sort of).
Dan =0)You can help me save the Earth from a terrible experience... yes, the whole Earth.
Self-plug #2: http://blog.myspace.com/dankupkamusic