Backup compression doesn't work

Please help. I've created Sheduled Backup, it's all ok except compression. Backups are made by tar, and gzip or bzip2 doesn't work.

I switched in Module Config compression method, it does nothing.

I'm using CentOS 5.2/5.3 everywhere,
virtualmin installed through
after basic OS installation. Compression method is gzip in Module Config, all backups are scheduled, in one single archive, then copy through SSH to another server.

Copying virtual server configuration ..
.. done

Backing up Cron jobs ..
.. none defined.

Creating TAR file of home directory ..
.. done

Saving mail aliases ..
.. done

Saving mail and FTP users ..
.. done

Backing up mail and FTP user Cron jobs ..
.. none to backup

Copying records in DNS domain ..
.. done

Copying Apache virtual host configuration ..
.. done

Copying Apache log files ..
.. done

Copying Logrotate configuration ..
.. done

Creating final backup archive ..
.. done

Uploading archive to SSH server ..
.. done

6 servers backed up successfully, 0 had errors.

Backup is complete. Final size was 801.68 MB. Total backup time was 20 minutes, 49 seconds.

Sent by Virtualmin at: https://xxxx:10000

Closed (fixed)