Thanks guys. This guy's network is so basic, but you never know. I'm only now realizing that I didn't ask him if he had a wifi repeater somewhere or something, but given how much this guy overshares information I would think he'd have mentioned it by now. And yeah, the fact that he's replaced the modem AND router three times really has me puzzled. He keeps assuming it's his computer, but it seems pretty clear to me that it isn't.

I'm really thinking it's environmental. Either wavering power or wavering signal on the coax. He *thinks* that this issue started about 3 years ago after a storm caused an electrical surge in the house. To which I'm thinking "uh, yeah, that could do it," but I don't know where to begin and he seems reluctant to do much about those lines...