So, I did not rename the content folder. The strange thing is that I have the problem to only one of my computers and only with Firefox. The IE shows the "Explorer" view to normal.
I think it could have something to do with cache- and or localstorage items. Try to empty your browser cache, or better try to login via a NEW PRIVATE WINDOW:
You might need to open "developer tools" and delete variables in your localstorage: