Thread:Project:Support desk/Special:UserLogin only displays "you have to log-in message"

I have a private wiki for registered users only. After a site-crash, the latest backup was restored. Now, when I click on "Log-In" oder go to the Special:UserLogin page, I just get the "you have to log in"-message - with a link to Special:UserLogin. I.e. I'm never shown the form to input my credentials. Any ideas what could be messed up?