Backup Strategy Not Working

[Graham Watkins]

Hello All,

I have been running an automatic backup of my home partition using a tar 
command which runs as a scheduled task once a week.

The command is as follows:

tar -cvpzf /media/graham/Expansion\ Drive/graham.tar.gz /home/graham 
--exclude "/home/graham/VirtualBox VMs"

Anyway recently I had reason to access the tar.gz file created by this 
command and using Archive Manager, I attempted to open the tar.gz file.
It would not open and I received the following error message:

gzip: stdin: invalid compressed data--format violated
tar: Unexpected EOF in archive
tar: Error is not recoverable: exiting now

I have found that If I run the command from a terminal. the file can be 
accessed without problems.

To sum up, it seems that I do not have the backup strategy I thought I 
had and this is somewhat disturbing.

Does anyone out there have a clue as to what the problem might be and 
how it can be fixed?

Failing that, can anyone suggest an alternative backup method that 
avoids this problem?

Any advice would be appreciated.

Cheers,

Graham