phpBB installation troubles

I did the prerequisite searches for this issue and came up empty.

I have an existing Zen Cart install to which I am adding a phpBB forum. I uploaded all phpBB files into a directory called "forums", and I was given the correct "Welcome to phpBB 2 Installation" page. I was asked for the database name and all the username/password info, and upon confirming the information and clicking the "Start Install" button, I am sent to a page that says:

"Your admin username has been created. At this point your basic installation is complete. You will now be taken to a screen which will allow you to administer your new installation. Please be sure to check the General Configuration details and make any required changes. Thank you for choosing phpBB 2."

That text is followed by a "Finish Install" button. I click the button and I'm sent to /forums/login.php, where Zen Cart then throws me a couple errors:

Warning: require(includes/templates/template_default/templates/tpl_500_default.php) [function.require]: failed to open stream: No such file or directory in /home2/trishcom/public_html/includes/templates/classic/common/tpl_main_page.php on line 128

Fatal error: require() [function.require]: Failed opening required 'includes/templates/template_default/templates/tpl_500_default.php' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home2/trishcom/public_html/includes/templates/classic/common/tpl_main_page.php on line 128

Any experience with this?

Would it be better to put the forum into a sub-domain?

empirenine:

includes/templates/template_default/templates/tpl_500_default.phpI don't know where you got that from. It certainly isn't part of the Zen Cart core files.
Perhaps you're attempting to use a contribution that's not fully installed or properly configured?