Page Tab not recognized for some pages

After some time I got the themes for the tabs to work, but not for the node edit forms... The problem is, that in the fb_is_tab() function the page is not recognized as tab. There is no $_REQUEST['signed_request'] and the $_fb is still undefined. It probably has to do something with URL rewriting, if I understood it right. Anybody facing the same problem or some hints on how to solve it?

p.s. I had also the problem that the page-tab theme was not rendered and then I had a blank screen like some other users... I solved it by changing this in the fb_tab.module:

function fb_tab_fb($op, $data, &$return) {
  $config = _fb_tab_get_config($GLOBALS['_fb_app']); // new line, config is not defined otherwise
  $fb = isset($data['fb']) ? $data['fb'] : NULL;

greetz