[Plugin: Background Manager] Backgroundmanager doesn't show custom background

I have uploaded a new custom background with backgroundmanager in the moonbeam theme.

It doesn’t show up on the regular pages but it DOES showup in the search and error page. Of course I also ticked the checkboxes for ‘front page’, ‘single page’, etc.

http://mtimmerfotografie.nl (no custom background)
http://mtimmerfotografie.nl/doesnotexist (DOES show custom background)

Any clues?

http://wordpress.org/extend/plugins/background-manager/