What Happened To My Alexa Stats?

While you were checking your websites during this week, have you noticed something wrong? Did you see a weird change in your Alexa numbers? I was surprised that my Alexa numbers in my websites were back to the previous month's stats. It is not convincing to see my websites' back in the last month's ranking because they are receiving consistent traffic everyday. I have no idea what is happening with Alexa's updates. Do you know?