Repeating error message "Backup failed" for a cancelled backup

I cancelled a hard disk backup task a few weeks ago and replaced it by another one with another name. The new one is running perfectly, the old one was deleted from the list of available backups, I don't see it anywhere any more which is fine.

However, whenever I boot the computer, I get an error message that the backup for the old task failed; for explanation it refers to the action log, but there is no entry in the action Log. Obviously the old task still exists anywhere and the program tries to start it?!?!?

Has anybody an explanation?
Thx, Thomas.