After a week of the cable modem being up, down, up, down, up when I'm on the phone with tech support, down when I get off the phone with tech support, etc., etc., etc... I was finally able to get on the phone with tech support while they were actively monitoring my cable modem while the damn thing connected and disconnected at least three times.
They now agree I have a problem. :)
The lady on the other end of the phone noticed that their monitoring system was showing some very strange power fluctuations, and they'll be sending someone over to look at it more closely either today or tomorrow. Meanwhile, I fully expect a dimensional rift to spawn outside my bedroom window, sucking my wife and I into an alternate universe where I have grown rich licensing my comic to consultants who train marketing and legal departments in large corporations all across the computer industry.
In this alternate dimension I have a goatee and a private dirigible. Naturally.
Meanwhile, in this dimension, my internet access is still spotty.