Looks like we have reports via WebmasterWorld starting a few days back of a Google PageRank update.
I am not getting in the debate of how important PageRank is or is not. I discussed PageRank over here so that I don't have to mention it in every PageRank article.
So there seems to be a PageRank update taking place. This is just a toolbar PageRank update, so do not expect your rankings to suddenly change.
Forum discussion at WebmasterWorld.