Non preoccuparti più di tanto degli "strani" comportamenti: sono in corso degli aggiornamenti all'infrastruttura di Google. Ne ha parlato ad inizio mese anche Matt Cutts (More info on PageRank):

... I think most data centers are running the newer infrastructure for things like info:, related:, link: and PageRank, and I believe every data center that has that newer infrastructure has the recent snapshot of PageRank now. I wouldn’t be surprised if it took at least 1-2 months for the other data center IPs to get the newer infrastructure in some way...