All access to admin functions of my client's site are gone! Can't change a thing anymore ...
Started the plugin, clicked OK on the popup and waited. Nothing happend, the loading wheel kept spinning. Eventually I tried and hit the X. The window closed. No error message. I figured everything is fine.
Then I made changes to some roles. Not to admin rights, though. But as I hit the SAVE button I saw that - while I thought I had switched roles all the while using the buttons on the bottom of the main frame - my active role had actually remained Admin. So all changes where saved for Admin. And all my admins. No Superadmin got created.