Wrong order

Hi,
I installed your plugin on my site http://ilustrator.cz/ and use the widget in the right column and in the footer. At the beginning, it was ok, but the next day the order was wrong – on both places the articles are ordered according to publishing date and not according to popularity. When I use the EMPTY CACHE button all looks ok for the first day, but the next day it is all ordered again according to publishing date 🙁

I don’t use any cache plugin.

The setting for the widget in right column is:
Show 7 posts, Last 30 days, Total views. Filters: post, Display post thumb. That’s all!

Can you look at it? Where can be a problem?

http://ww.wp.xz.cn/plugins/wordpress-popular-posts/