Fieldable pane content not displayed

I have the latest (downloaded today) -dev versions of fieldable_panels_panes, ctools and panels. I can easily create new entities through the panels interface, and view/edit them under the entities list. However, the panel content is not displayed, and after saving an entity, panelizer displays 'Placeholder for empty "No title"'. (Tried it with a standard page handler page as well)

Unfortunately, I'm not familiar enough with the guts of panels/ctools to easily debug this. I can tell you that the result of a func_get_args() in fieldable_panels_panes_fieldable_panels_pane_content_type_render() is the following:

(Array, 5 elements)
0 (String, 21 characters ) fieldable_panels_pane
1 (Array, 0 elements)
2 (Array, 0 elements)
3 (Array, 0 elements)
4 (String, 0 characters )

thanks much for all you do, this is a great module with a lot of potential!