Can't login all of a sudden??
I'm on a deadline with a client and this puts a major wrench in things.
What is C5 version and url
Are you logging in with the right email and password?
I just realized, I don't know how to upgrade the site to 5.6 without being logged in either...
How was the custom log in page produced?
You don't need to log in to upgrade to 5.6, do it from the server and just replace the 'concrete' folder.
Long week. Sorry for wasting anyone's time!