No tracking after upgrade

Hi, I’ve two wordpress installations on the same server running. After upgrading both didn’t track anyting. I disabled and enabled the java script and finally one installation worked again.
The other one was hopeless. What I did by the non working – uninstalled the whole thing deleted all data an reinstalled it again. Now it does track something – but only with disabled java mode. But to my surpris it shows the “a misconfigured setting and/or server environment is preventing WP SlimStat from properly tracking your visitors” message. But like I said – both installation have a different layout and one or two different plugins – but generall configuration is pretty much the sam.
Now I’m helpless – any Idea how I can bring that plugin back to work?

http://wordpress.org/extend/plugins/wp-slimstat/