guest checkout don't work

I activated the Guest checkout. But when I'm at the guest checkout and fill in the e-mail adress and press "Registration" button. I get redierected to the main page. Something goes wrong, but I don't know what.

username hikaadmin
PW phahR1aW

Hello,
Can you try it with a custom "checkout" menu on the "Force a menu on the checkout" option via "Hikashop->System->Configuration->Checkout"