Membership giving to non-admin users on pictures and files hosted under wp-content/uploads

Hello,

On my site, pictures uploaded through the default WP uploader are not showing up to non admin users, even though I don't have membership download protection setup. Here's a sample: http://ecrp.pottervilla.com/hello-world/ . (pictures on other pages of the site I uploaded to a different directory, and they are no longer affected). When you click on a picture to view it, you get this error: Warning: strstr() [function.strstr]: Empty delimiter in /home/ecrp/public_html/wp-content/plugins/membership/membershipincludes/classes/membershippublic.php on line 422
404 — File not found.
(from this link: Warning: strstr() [function.strstr]: Empty delimiter in /home/ecrp/public_html/wp-content/plugins/membership/membershipincludes/classes/membershippublic.php on line 422
404 — File not found. )

I disabled all my other plugins (even WPMUDev ones) and switched back to TwentyEleven, but it didn't help. I also deleted the membership plugin and started over, but that didn't help.

Does that sound like a bug? Would you fix it?

Thanks!

- Jonathan