Ping *now* shooting up to 100 over expected.

Hi, people. I'm not gonna basically go "PLZPLZPLZPLZ Sum1 GET MA PING-AGE BAK 2 NRMAL ty". I'm not one of those people.

A while back - when the West Coast first came out, I had ping of about 190 - expected from a below-average ISP in New Zealand. Then it dropped for a few days to ~163, the ISP must've landed on its feet. And, after doing a few surveys/d-loads.. my ping shot up to (either) 174, to 200. And just checking today, it's now from 200-270!! How is this happening?
I would like a few tips, or possible solutions on why this is happening... spyware? Viruses? A hobo with a laptop on the street outside downloading "adult material"?