google pulls its results from numerous datacenters, they
generally show the same serps but when things change it takes awhile to come across all dc's. I often see sales from serps that i cant see here at home. Then a day or few hrs later it appears in my results.
check out
http://www.seochat.com/seo-tools/pagerank-lookup/ and look at the future page rank checker...run a url through it, it shows results from the google ips, (datacenters) then you can check them each by ip if you want.