Just a couple of weeks late on this one.... there was a PageRank update a couple of weeks ago. I'm not sure of the exact date, but have logged it as 4/26.
What to do: Log it for trending. Compare current PageRank with historical PR scores. Consider it an indication of your SEO going up or down.
Remember: This is not reflective of traffic today, or the past couple of weeks. It's old data.