Seems like some people are reporting fluctuations in the PageRank indicator within the Google Toolbar.
Now, I am not sure if this is just a minor update or the start of a larger Toolbar PageRank update. Either way, I wouldn't worry.
The last update we saw was in January 2011 and as I repeated then, "Google keeps telling them not to worry about PageRank but SEOs don't hear or listen. They think SEO is all about PageRank, when you and I know it has very little to do with PageRank. Especially Toolbar PageRank which is a fictional character used by Google's marketing department."
So do not worry but if your PR went up, congrats! If not, who cares!