ERamseth on "can't get checkAccess() to work"

So I've written a script which serves videos to jplayer from a directory that isn't normally visible to web browsers.

I'm trying to incorporate checkAccess() into the script so it can only pull files for a user who should be able to access said files.

So far I've added

define('SERVERPATH',str_replace('\\','/',dirname(__FILE__)).'/zp');
define('WEBPATH','/'.basename(dirname(__FILE__)).'/zp');

require_once(SERVERPATH.'/zp-core/template-functions.php');

to my script and have done

zp_load_gallery();
zp_load_album('$albumName');
zp_load_image($albumName, $imageName);

with valid directory and file names.

when I try

print $_zp_current_image->checkAccess();

I never get a result (I assume that means it thinks I don't have access). I have tried it both logged in and logged out and it makes no difference. I know the $_zp_current_image seems to be working in other areas... I can get valid width and height; and isProtected() returns 1.

Is there anything glaringly wrong with what I've done in my code that might be causing me problems?