Due to release of Django 1.4 the integration instructions of Apache and QuintoLabs Web UI has been updated. For example for CentOS it is now (note ==1.3.1 at the end):
#yum install httpd mod_wsgi python-setuptools
#virtualenv --no-site-packages qlproxy_django
Thanks to Pete and Kees for bug report and fix instructions!
The error that comes out after old integration steps is:
ImportError at /
Import by filename is not supported.