I noticed in IE6 there is a JS error because of an dangling comma at the end of the MCE init params object.
Here is a fix at line 247 of TinyMCEComments.php which had this:
foreach ( $initArray as $k => $v ) $res .= $k . ':"' . $v . '", ';
$params = array(); foreach ( $initArray as $k => $v ): $params = $k . ':"' . $v . '" '; endforeach; $res = join(',', $params);