Problem with wordpress.com stats

Hi there, from this mourning I have a problem with wordpress.com stats: there are stats for the most frequently visited posts that put posts that are not visited in the last 10 months or so and the most recent ones and the ones visited in the last month is not there…
Is that some kind of virus or problem on wordpress.com?
Please answer me because I love the feature of the most visited posts on my blog and now I had to remove it…