I have noticed that Google shows different web site positions for the same keywords if I searching from different PCs. How can this fact be explained?
Over the last few days I've been able to refresh search results from 1 PC and get different results, could be getting them from different servers at Google's end? Maybe Google is updating something.
Different datacentres is a possibility but personalised search is most likely what you're seeing. We're getting to the stage where rankings are meaningless because everyone sees their own SERPS.