Prueba en libraries/joomla/database/table/user.php linea 158:
if (eregi( “[“‘%;()&]”, $this->username) || strlen(utf8_decode($this->username )) setError( JText::sprintf( ‘VALID_AZ09’, JText::_( ‘Username’ ), 2 ) );
return false;
}
Introduce ahi tus simbolos prohibidos.
