hi, do you have tried this? (from the FAQ)
When trying to access amy of the SlimStat options in the backend, I get the following error: You do not have sufficient permissions to access this page.
You were playing with the plugin's permission settings, weren't you? But don't worry, there's a secret passage that will allow you to unlock your access. Create a new user slimstatadmin, and assign him the Administrator role. Then log into your WordPress admin area with the new user and... voila: you can now access WP SlimStat's settings again. Update your users' permissions and then get rid of this newly created user.
For me WORK!