londrum - 9:12 pm on Nov 1, 2012 (gmt 0)
if the site's IP address changed then maybe google reset all the site's data. (it sounds a bit wierd... surely they would go by the domain name? but who knows how they work.) so they might not know what the best performing ads are anymore. it will probably work itself out if you give it enough time.
if it was me, i wouldn't go changing anything just yet, in case you unwittingly change something that is actually working okay