Fallo en la consulta:
'SELECT * FROM doc_documento_extra WHERE usu_usuario_id = '424' GROUP BY doc_documento_id ORDER BY CAST(fecha_descarga AS UNSIGNED) DESC
array(3) {
[0]=>
string(5) "HY000"
[1]=>
int(1030)
[2]=>
string(32) "Got error 28 from storage engine"
}