Can not cancel sbackup

Started sbackup as root "gksu sbackup-config-gtk ".
While im trying to cancel a backup job it asks for a password. When i use my user password what i used to start sbackup, it pops up a message " Unable to cancel backup process".
With root password it says " Invalid password".
There is nothing in the logs.
How can find out why it can not cancel the running backup process?