It seems a plugin conflict, after I renamed the plugins directory(this disable the plugins temporarily) I manage to get in the admin.
https://www.dropbox.com/s/r489b3roz1jly9r/Screenshot%202015-09-16%2012.20.07.png?dl=0
I activated again the other theme.
Go to the plugins and deactivate them all, then switch to Dante theme and activate 1 by one until you get the blank page and find the problematic plugin.
-Rui