Mezzanine only loads admin pages on debug
A couple of months late, but for posterity: I found the same issue with Mezzanine 4.3.1 on Heroku. Without delving under the hood of the Mezzanine source code, using version 4.2.3 works fine.
I have a Mezzanine blog under development, hosted at Heroku.
While I have it on debug mode, by ensuring settings.py has DEBUG = True, everything works like a charm.
When I set it to false, any attempt to access admin gives me the generic error message. All other aspects of the site works fine, including blog posts I've made (with DEBUG = True) for testing.
I'm looking for any of two forms of help:

How could I get better debugging information while having DEBUG =
False in settings.py?
Any hint or suggestion about what could be the problem.

Edit: My static files are being served with White Noise, locally, without any problem.