Ok. Thanks for your response. I've worked out what the issue is and basically the changes made in 1.4.3 to functions-basic.php have made it impossible to now include that file from a standalone page outside of the main zenphoto folder.
Is there a reason why the way the paths are worked out was changed from this:
dirname(dirname(__FILE__)) . '/' . DATA_FOLDER . "/zenphoto.cfg"
to this:
$const_serverpath.'/'.DATA_FOLDER."/zenphoto.cfg"
where $const_serverpath is worked out using the script filename, which is the filename of the script that does the include.
$const_serverpath = str_replace('\\','/',dirname($_SERVER['SCRIPT_FILENAME']));