the error in the error.log:
"client denied by server configuration: proxy:http://"
The problem: debian has a proxy.conf file in /etc/apache2/mods-enable, which sets "Deny from all" as default. This will screw you over.
Words and solutions take from here: http://mail-archives.apache.org/mod_mbox/httpd-users/200307.mbox/%3c20030723191854.43885.qmail@web40903.mail.yahoo.com%3e
