I don’t know if will work for you, seems that is missing the tinymce editor so I commented the line 237 and the warning dissapear, I know is temporary but at least it let me work
//include_once (dirname (__FILE__) . ‘/admin/tinymce/tinymce.php’); // 22.408
Regards and good luck
It happen to me the same way (the html link did not make the switch), I do not know if there an issue with the NextGen Gallery, but once I deactivated , it works for me ,what I did is to deactivaed all plugins and reactivated one by one then I found that did not work with the NetGen Gallery.
I do not saying that the plugin is the culprit, but just check it !
Regards
