Thanks guys, not sure how I missed that. Changed to PHP 5.4 but no difference in behaviour. Any help you can give with the scripts would really be appreciated. Here's some more detail. I'm installing the ORS resource scheduler (http://ors.sourceforge.net) latest version 3.8.1. The first stage of install is at scheduling/install/index.html and clicking on the start install link works fine, bringing up the page at scheduling/install/install.php which identifies the PHP version (so basic PHP is definitely working) and says step 1 is complete. But here's where it starts to go wrong. The next link goes to scheduling/upgrade.php, but here I just get a blank page in FIrefox. Using 'wget -S' to retrieve that page from a Linux command line, I just get a 500 Internal Server Error with no content. Using cPanel to check the error logs, I see no errors at all. Presumably something is up with upgrade.php, but I can't see what...