OK I just did this locally and this is the result for the configure.php entry:
Code:
  define('DIR_WS_PHPBB', 'phpbb/');
My directory for the forum sits with the Zen Cart files in a folder named phpbb

You have it installed with/in a folder named "forum"

so change what I incorrectly posted earlier to:
Code:
define('DIR_WS_PHPBB', 'forum/');
And see if that corrects it. This is due to the heading in the configure.php file for these entries that states:
// NOTE: be sure to leave the trailing '/' at the end of these lines if you make changes!
// * DIR_WS_* = Webserver directories (virtual/URL)
// these paths are relative to top of your webspace ... (ie: under the public_html or httpdocs folder)
And not as the next set of entries requires which is this:
// * DIR_FS_* = Filesystem directories (local/physical)
//the following path is a COMPLETE path to your Zen Cart files. eg: /var/www/vhost/accountname/public_html/store/
Which is what you are attempting with:
Code:
	define('DIR_WS_PHPBB', '/home/C/csstempl/www/forum/');