Bandwidth

So my ISP recently made an upgrade in our area, or so they said. A week ago the internet was out a good percentage of the day, when it came back, all hell broke loose.

I have 5mbit down, 256kbit up. But this is what I get between 7am and 1am:
(speedtest img missing, thx dslreports.com)

And this is what I get between 1am and 7am (a whole 6 hours a day):
(speedtest img missing, thx dslreports.com)

As you can tell, the upstream is consistent, but the downstream is on crack.

Cable internet is a shared network. At first I had good speeds all the time. Apparently someone on the node closer to the ISP than me decided it would be funny to stream some HD pr0n or something. Anyway I don't mind the speeds at night, but I would prefer a more stable connection. Especially since I'm paying more than most, and most likely paying more than the guy on the node who is stealing my bandwidth.

They said they are aware of the issue and are working on it, but I don't know. How do you leave an entire node uncapped for a WEEK?