Upgrading WP and problem with stats

I’ve a strange visualization on my websites after updating the stats.

Now I see only the bar, not more the line as before, and no informations on the last two days as before.

I can see the “today” stats by pressing “views today” but it’s now impossibile to see the stats about one week, month and so on.

Can you help me? What’s happen?

Thanks to all.

(the same problem on a website with wp 2.9)

http://ww.wp.xz.cn/extend/plugins/stats/