[FLOW3-general] Blog example login: No login form - error instead

[Jens Hopp]

Hi

playing around with the blog example this is happening:
When I click on "Login" /typo3.blog/admin should be opened but no 
login form is displayed (I think this should happen?). Instead I'm 
immediately redirected to /flow3/authentication displaying this error: 
"An error occurred while trying to call 
TYPO3\FLOW3\Security\Authentication\Controller\AuthenticationController->authenticateAction()."

I use beta2.

Thanks a lot for any hint.
Jens