We had this issue in the office, as we are dealing with many types of malware and viruses we were sure that we have some kind of bot in the network, we traced some queries to google from one VM, than killed it and the requests started coming from other VM and so on.<p>Eventually we were able to pinpoint this to specific toolbar that was bombing Google with PageRank requests.<p>After removing this toolbar- all went back to normal, so perhaps some users that using the same VPN provider are using some sort of tool and abusing google.