The increase in dispatch errors reported by BIND recently is explained by the other ISC here; http://isc.sans.org/diary.php?storyid=1538 So it looks like the error message was right, although some older versions of BIND didn't do a good job of reporting the IP addresses involved. My own experience was the servers mentioned here aren't the only servers doing this rather bizarre behaviour, but it is likely they could account for the increase seen (in association with a spam run causing lookups).