(DOCUMENT_ROOT) I thought that used to show up in the System Info portion of the Joomla backend but my quick check I did not see it...
Changes those 2 lines previously mentioned to be
[code:1]$phpbb_root_path = "public_html/phpBB2/"; [/code:1]
(or whatever the path needs to be incase if goes deeper than public_html)
on the "DOCUMENT_ROOT"... to see it we can add a quick temporary line to phpBBgui.php... say right after the line above
[code:1]die("DOCUMENT_ROOT = ".$_SERVER);[/code:1]
once you save this into phpBBgui.php try to go into the phpbb connector control panel... when loading it should stop and say
DOCUMENT_ROOT = xxxxxxx
Copy this line of text and post it into another message here... then remove the die() line from your code... and the connector should be working again.
Greg