I installed the mod with no errors or problems. But when I get into my ACP and click the tab to set the settings I get this error message:

[phpBB Debug] PHP Notice: in file /phpbb_seo/phpbb_seo_class.php on line 822: file_exists() [function.file-exists]: open_basedir restriction in effect. File(/phpbb_cache.php) is not within the allowed path(s): (/var/www/vhosts/mydomain.com/httpdocs:/tmp)

Is it some security measure that's blocking me from running it or something?

My first quess would be that for some reason files did not upload
the file it is looking for is /includes/acp/acp_phpbb_seo.php

If only everything was that easy

I had a look at your link and you can scroll to the right about 6 feet on your site
You might want to re look at what you have edited, should be near the rrs feed code ?

I may have had a permission problem that prevented some files from being placed, but when I actually investigated the issue now I seemed to miss a file called phpbb_seo_meta.php and that file wasn't even in the package I downloaded. It was in another package (the pre-mod one).

Pretty confusing stuff. But I'll try and get it configured now, as I for the first time get the configuration screen