Membership download obfuscation probLem

OK, so I downloaded the "Add To Server" plugin and added all my 100MB files to the media library.

I set up the membership plug-in to use an obfuscated download link...

I went to my post page and used the URL

http://channelrobot.com/obfuscated/bigfatfile.rar

when I go to the site page I get the above URL for the file, (all good so far)

I click on the file and get:

Fatal error: Call to a member function has_level_rule() on a non-object in /home/channelr/public_html/wp-content/plugins/membership/membershipincludes/classes/membershippublic.php on line 318

...any ideas?