No ftp backups. Error with backup.pl

I scheduled a task for backup all servers o 04:00 and 15:00 every day over a ftp server.

But this task not work all times. Many times only create directory on ftp server but it's empty.

I have found only 1 error in the system logs, in the file /var/log/syslog:

3315:Sep 2 15:00:32 host01 kernel: grsec: failed fork with errno -12 by /usr/share/webmin/virtual-server/backup.pl[backup.pl:1809] uid/euid:0/0 gid/egid:0/0, parent /usr/sbin/cron[cron:1808] uid/euid:0/0 gid/egid:0/0
3316-Sep 2 15:00:33 host01 last message repeated 4 times
3317-Sep 2 15:00:33 host01 kernel: grsec: more alerts, logging disabled for 10 seconds

Status: 
Closed (fixed)