Using wordpress-sql-backup 7.0.
My host has disabled passthru(), system() and exec().
The plugin does not gracefully handle this scenario and keeps the nagging errors about the settings being empty.
Although it is a lot of work for you, it would be best to use a purely php method to backup the database (phpmyadmin's export code would be a good starting point) and the files (e.g. Archive::Tar PEAR package: http://pear.php.net/package/Archive_Tar/ ).