Index: wp-admin/admin.php
===================================================================
--- wp-admin/admin.php	(revision 6794)
+++ wp-admin/admin.php	(working copy)
@@ -53,7 +53,7 @@
 			wp_die(__('Invalid plugin page'));
 		}
 
-		if (! file_exists(ABSPATH . PLUGINDIR . "/$plugin_page"))
+		if (! ( file_exists(ABSPATH . PLUGINDIR . "/$plugin_page") && is_file( ABSPATH . PLUGINDIR . "/$plugin_page") ) )
 			wp_die(sprintf(__('Cannot load %s.'), htmlentities($plugin_page)));
 
 		do_action('load-' . $plugin_page);