Trying to install on Apache server with cPanel.

I have PHP 5.4 and 'session.save_path' is set.

Any ideas?

I think the session is not being saved.
try creating a PHP file test.php

<?php

session_start();

if(!isset($_SESSION["count"]))
{

$_SESSION["count"]=1;
}else{

$_SESSION["count"]++;
}

var_dump($_SESSION["count"]);

?>

try refreshing the page 3-4 times, if you see the number increasing, then session is working perfectly, else there is some problem in your PHP SESSION configuration.

I was trying to run the installer form it's sub-domain, as opposed to it's directory listing, so it's installed now, however, I'm not getting this error (only on the fronted, I can access all the backend with ease and no errors);

"Fatal error: Call to undefined function Controller_() in ........websiteurl"

if you can tell us the line number and filename from the error, it will help us to pin point the problem