Here's a video which hopefully will better explain what is going on.

http://thehowards.ca/images/pingplotter2.mov

You will see that in the list if IP addresses, hop 1 alternates between 192.168.0.1 (presumably the modem) and 10.75.224.1 (the same IP as hop 2).

I can't replicate my earlier experience where Hop 2's chart would not show a ping when hop 1 is pinging the modem. Well, as I write, that has come back after a fashion, pinging 8.8.8.8. But now I get three pings of both hops 1 and 2. On the next ping hop1 is greyed out and hop 2's ping time goes from an average of about 10ms to somewhere close to 200ms.

This behaviour happens for about 1m30s then stops for about 2m on a very predictable cycle.

What could be causing this in the network, or is it an artifact within PingPlotter?