Call to undefined function fieldable_panels_pane_view

I'm sorry, what fatal error do you refer to? Are you making a change because the metadata module is hardcoding what the names of our view callbacks should be? I'm very confused by this change.

So here's the irony: The Entity API module has Field API formatters which allows you to select a formatter to render an entity through a view mode. The callback for that is entity_metadata_view_single(), however, it looks at the entity_type name - see below. In case of the fieldable panels panes module, the entity key is 'fieldable_panels_pane', but the callback to view it is 'fieldable_panels_panes_view', that's why the undefined function error pops up.

function entity_metadata_view_single($entities, $view_mode = 'full', $langcode = NULL, $entity_type) {
  $function = $entity_type . '_view';
  $build = array();
  foreach ($entities as $key => $entity) {
    $build[$entity_type][$key] = $function($entity, $view_mode, $langcode);
  }

  return $build;
}

I haven't tested whether it's possible to change the view callback in the entity info to fieldable_panels_pane_view, but I hope this info makes it a bit clearer?
(note, it probably happens in other occasions as well outside field api formatters, but not sure)

Yes it should be possible to change this in the entity info somewhere. I'd start by trying 'view callback'?

zuuperman is correct: it looks like the view callback is given an array with one entity. I've adjusted the fieldable_panels_panes_view() function to react accordingly if the argument is an array. I'm not sure if this is the best way to deal with this.

This change looks acceptable and allows compatibility with entity API, so committing to #8 to 7.x-1.x. http://drupalcode.org/project/fieldable_panels_panes.git/commit/4031576

Committing #8 made fieldable panel panes incompatible with the 'Rendered entity' row plugin in Views.

Fixed for real with http://drupalcode.org/project/fieldable_panels_panes.git/commit/cd4949f