Hello !

Could not find the bug tracker if any. There is a bug in the file inclusion for component own sef_ext file in joomsef.php, line 459 :
// If component has its own sef_ext plug-in included.
if (file_exists($GLOBALS['mosConfig_absolute_path'].'/components/$option/sef_ext.php')) {
// Load the plug-in file.
require_once($GLOBALS['mosConfig_absolute_path'].'/components/$option/sef_ext.php');

$option is not interpreted (for file_exists and require_once) because the string is in sinlge quotes. Should be double quotes or xxx'.$option.'yyy