When attempting new user authentication via Kerberos ticket, the Login button in the corner causes Zanata to render a mostly blank page, instead of logging in and redirecting to the original page. (I think it was trying to render the first-time login/registration screen, which asks for name, username and email before logging in "completely".) (See screenshot zanata-blank-klogin.png)
After registering the account in another browser (using username / password login instead of ticket), the original browser would successfully log in, but again the page was mostly blank. (See Screenshot_2016-05-03_17-32-21.png) This part is easier to reproduce than the new user experience above, because it doesn't require a brand-new account, but I think the cause is probably the same.