Is this some kind of "cable slowdown"?

A few days ago I started having problems with my Cox HSI service. Things will be going along just fine, and then everything slows to a crawl. A multi-ping test to my default gateway during these bad periods yields packet loss of 30-60%. So it's no wonder nothing works.

And then when I come back to the computer an hour later, everything may be fine again. There has been no reset, power cycle or reboot of either my computer or my modem in the meantime. I've tried using my old computer, but it does the same thing. I don't have an extra modem to switch out.

And rebooting/resetting doesn't help.

Even more testing shows that the power levels and SNR ratio are the same whether things are fine or awful. The up and down frequencies are always the same - 25 and 663 MHz.

The modem is a Toshiba PCX2200 which has worked great for several years.

Does this look familiar to anyone? The tech is coming out Monday, and I just know it will be working perfectly when he's here. What do I need to ask him to check?

Someone suggested it might be a P2P d00d on my node who's found a way to remove the speed limits on his modem, particularly the upstream limit. Another thought was possible interference from someone's cable phone service - that could explain the timing I'm seeing.