suPHP causing server 500 errors

[djh-compnet]

First of all thank you to the developers for this brilliant control panel.

The suPHP module version 0.6.3, default Debian one not compiled version, Apache 2.2.9, PHP 5.2.6-1, and ISPConfig 3.0.1.2 are installed on Debian Lenny.

This is a custom virtual host with SSL and the port 80 one is virtually the same without the SSL directives.

<VirtualHost 123.12.123.12:443>
        ServerName domainname.com
        ServerAlias www.domainname.com
        ServerAdmin webmaster@domainname.com
        DocumentRoot /var/www/domain/public_html

        SuexecUserGroup www-data www-data
        <Directory /var/www/domain/public_html>
        Options FollowSymLinks
        AllowOverride Indexes AuthConfig Limit FileInfo
        Order allow,deny
        Allow from all

        suPHP_Engine on
        #suPHP_UserGroup www-data www-data
        AddHandler x-httpd-php .php .php3 .php4 .php5
        suPHP_AddHandler x-httpd-php
        </Directory>

        SSLEngine On
        SSLCertificateFile /etc/apache2/ssl/www/www.domain.crt
        SSLCertificateKeyFile /etc/apache2/ssl/www/www.domain.cert.key
</VirtualHost>

If you are wondering whether it is the custom vhost that could be causing it, well, the same 500 server error happens with sites enabled with the ISPConfig control panel with suPHP enabled.

This is the suphp.conf:

[global]
;Path to logfile
logfile=/var/log/suphp/suphp.log

;Loglevel
loglevel=info

;User Apache is running as
webserver_user=www-data

;Path all scripts have to be in
docroot=/var/www

;Path to chroot() to before executing script
;chroot=/mychroot

; Security options
allow_file_group_writeable=true
allow_file_others_writeable=false
allow_directory_group_writeable=true
allow_directory_others_writeable=false

;Check wheter script is within DOCUMENT_ROOT
check_vhost_docroot=true

;Send minor error messages to browser
errors_to_browser=false

;PATH environment variable
env_path=/bin:/usr/bin

;Umask to set, specify in octal notation
umask=0077

; Minimum UID
min_uid=100

; Minimum GID
min_gid=100


[handlers]
;Handler for php-scripts
x-httpd-suphp=php:"/usr/bin/php-cgi"

;Handler for CGI-scripts
x-suphp-cgi=execute:!self

Basically what I need is a good solution to securely run PHP for MODx or Joomla with either suPHP or fast-cgi without having to chmod directories to 777 which surely is a security risk. The files and directories in public_html are owned by a apache user with uid/gid 1***/1*** and are also writable by the custom ftp user. I have scoured the forums for users that have had similar issues and tried various things to no avail. I would appreciate any help as this is now the only sticking point with my installation.