Redmine

Hi,

I've setup Redmine 2.1 on my Debian Squeeze server following this Tutorial HowTo configure Redmine for advanced git integration.
Redmine server is running properly, but I have a problem granting users to git repositories.

When I try to clone a repository it says:

error: The requested URL returned error: 500 while accessing

The apache error.log shows this entry:

[Fri Sep 28 15:50:56 2012] [crit] [client xx.xx.xx.xx] configuration error: couldn't check user. Check your authn provider!: /repo.git/info/refs

This is my apache configuration on git address:

<VirtualHost *:80>
    ServerName my.server.at
    DocumentRoot "/var/www/my.server.at/public" 

    PerlLoadModule Apache::Redmine

    <Directory "/var/www/my.server.at/public">
        Options None
        AllowOverride None
        Order allow,deny
        Allow from all
    </Directory>

        SetEnv REMOTE_USER=$REDIRECT_REMOTE_USER" 
        SetEnv GIT_PROJECT_ROOT /var/git/my.server.at/
        SetEnv GIT_HTTP_EXPORT_ALL
        ScriptAlias /git/ /usr/lib/git-core/git-http-backend

    <Location />
        Order allow,deny
        Allow from all

        AuthType Basic
        AuthName Git
        Require valid-user

        AuthBasicAuthoritative Off
        AuthUserFile /dev/null
        AuthGroupFile /dev/null

        PerlAccessHandler Apache::Authn::Redmine::access_handler
        PerlAuthenHandler Apache::Authn::Redmine::authen_handler

        RedmineDSN "DBI:mysql:database=redmine;host=localhost" 

        RedmineDbUser "user" 
        RedmineDbPass "password" 
        RedmineGitSmartHttp yes
    </Location>
</VirtualHost>

Environment:
  Redmine version                          2.1.0.stable
  Ruby version                             1.8.7 (x86_64-linux)
  Rails version                            3.2.8
  Environment                              production
  Database adapter                         MySQL
Redmine plugins:
  no plugin installed

It also asks me for user and password when cloning, but it shouldn't if I understand the tutorial right.
Can someone help me please and explain the error and what I can do.

Thank You!