imanager plugin stops FCK loading in Firefox

<?php
$oFCKeditor->BasePath = 'FCKeditor/editor/fckeditor.html' ;
$oFCKeditor = new FCKeditor('FCKeditor1') ;
$oFCKeditor->Value = $final_content;
$oFCKeditor->Width = "80%";
$oFCKeditor->Height = 400;
$oFCKeditor->Create() ;
?>