[Plugin: WPBook] Plugin not working. [Click permissions] failure.

Have you done this with total cache disabled?

Essentially WPBook works by sensing that it is being called from inside Facebook (based on the “signed_request” paramater Facebook passes in calling the iframe) and substitutes it’s own theme for your theme for that request.

For whatever reason that’s just not happening here – until this bit works nothing else will!

Given that you’re on one of the WordPress 3.0.x versions, it may be the issue other users reported, discussed in other threads.

Basically what you need to do is prevent the get_themes() call from happening at or around line 905:
$installed_themes= get_themes();

Easiest might be to just make the whole wpbook_check_custom_theme function return false – like this (note the lines starting with two slashes are commented out, and one new line added):

function wpbook_check_custom_theme($theme) {
	//$installed_themes= array();
	//$installed_themes= get_themes();
	//$wpbook_theme_check = (!empty($installed_themes[$theme])) ? TRUE : FALSE;
	//return $wpbook_theme_check;
     return FALSE;
	}