Enrolment

Hi, first of all I wan't to apologize because i'm not english native speaker. I apologize for any mistake I can make.

Well, my problem is the next, we're using 2.9 version in our company and now we are trying to use the Flat File Enrolment. But we find an error that can't solve it. I'm looking for some help because I don't know how to work it out, here is the error when I run the cron.php:

Running enrol crons if required...
Running cron for enrol_manual...
Verifying manual enrolment expiration...
...manual enrolment updates finished.
Processing manual enrolment expiration notifications...
...notification processing finished.
Running cron for enrol_flatfile...
Processing flat file enrolments from: $CFG->dirroot/matriculaciones/ ...
  Error deleting enrolment file: $CFG->dirroot/matriculaciones/
...finished enrolment file processing.
No enrolments to be processed in flatfile buffer
No expired enrol_flatfile enrolments detected

And the mail that sent, says (sorry I'm not a native english speaker son the message is in spanish):

El fichero de texto empleado en matriculaciones basadas en archivo
(/opt/apps/moodle/matriculaciones/) no puede ser eliminado por el proceso de
'cron'. Esto generalmente significa que los permisos son erróneos. Por favor,
corrija los permisos para que Moodle puede eliminar el archivo, de lo
contrario, podría ser procesado en varias ocasiones.

It says that the file in the directory can't be deleted by cron. Usually means there is something wrong with the permissions to moodle can delete the file. I change permision to 777, and is the same thing!

If anybody can help or have any idea about the error I would be very grateful.