I had the same problem!
My work around (by coincidence) was to use a different "Login Address".
Go to your QlikView Management Console > System > Setup > Manegement Service > QlikView Web Servers > click on your server > Authentication:
now you see in the bottom Login Address. In my case this was set to "Default Login Page (Browser Authentication)".
I changed this to "Alternate Login Page (Web Form)".
Reload the browser, login and it worked (in my case!?).
I don't really know if it will work for you, but you could give it a try!
Let me know if it worked