Summary stops counting visitors but Spy shows otherwise

I've been registered on here for approximately one week now. I love what your site offers and the details are invaluable. And I've been considering upgrading to your premium service. However, I've had a bizarre problem with my stats almost every single day with the exception of one day.

Your site seems to stop counting my visitors all of a sudden at a random time. And it's different each day. I can tell I am still getting many visitors by simply looking at the 'spy' section and can see that they are 'unique' visitors or first time visits almost every five minutes, but the are no longer being counted or appearing on the summary or visitor section.

Sometimes, it seems correlated with my first visit to the stats. In other words, it seems to have happened today. This morning at 8:30 am, when I first checked, my visitors are at 111, then as I continue to check, the number seems stuck at 111, even though 'spy' 'map' or cities', show me that many new and unique visits have occurred since I logged in. Now, it's 3 hours later and the number of visitors still reads 111 but it's very clear I have had at least 30 visitors since then.

Is this your server going down? How come in looking over the past week's summary of visits, the days the counter seemed to stop working, the bar is light blue, and the days that the counter seemed to work, it's darker blue?

Please advise.