FeedStats 3.4 seems to cause those troubles on my blog:
- Error 500 in the back office as I activate this plugin from the plugin page;
- Error 500 each time in the BO as I try to activate most of my other plugins.
- A plugin like Snap Shots doesn't work (no bubble, no preview while one goes on a link).
I have "resolved" the problem like this: plugin deleted...
(FYI : same troubles with any of the three latest versions of the All-in-one-SEO plugin.)