How can I upgrade?

How can I update Zencart via Fantastico> When I try to upgarde it this is the exact error log that I am receiving..

Upgrading....

Initializing Parameters - Done.
Generating MySQL Backup - Done.

Upgrade failed

The database fledger_zc1 is not working properly and the creation of a database backup file has failed. Please contact the sysadmin for further assistance. Include this message for reference.

The initial installation has not been modified.

I did a repair on the mysql database also. But no use.

Don't try to use Fantastico for upgrading. There are too many variables for it to be able to do it right. You need to update manually following the tutorials linked at the top of this page.