I want to have a login-page that uses my masterpage, but when I try to it goes crazy and writes out this URL:
I'm guessing (after some google-ing) that the behaviour is caused by AccessDenied exceptions..?
Should I just give up trying to use the masterpage or could I make it work?
I'm thinking this answer is too late for you, Jacob, but for anyone else who's finding this in Chrome, try clearing your cookies.
See here: http://karuppuswamy.com/wordpress/2010/06/17/how-to-solve-this-webpage-has-a-redirect-loop-error-in-google-chrome/
It could also be a problem with assets on masterpage with content that you do not hav access to? Make sure that data you have on masterpage is accesible without being logged on to the website.
EPiServer use common asp.net login features.