Strange behaviour (login works after one or two minutes)

I have a strange behaviour after loggin in. I use the correkt username and password, but after click on the send-button there′s still the login form. But after click on the send-button the cookies are set.

Than, after one or two minutes (the delay differs) and after reloading the page everthing works and I see the protected contents.

The page I need help with: [log in to see the link]