Incremental Backup: Operation has completed with errors. 5(0x640005)

I created a new incremental task but on activating start task get the message “Operation has completed with errors. 5(0x640005)”

I had to do a full recovery of my C disk as initially my PC would only allow me to log into Windows XP but then would immediately return to the log in screen. The recovery of the C: disk went well using Acronis True Image Home 11 (build 8,101). I can still make an incremental update with the old backup file. After creating a new backup file of the C: disk and validating the backup, I made a new incremental task but keep getting the error ““Operation has completed with errors. 5(0x640005)” immediately when running the start task. I ran Chkdsk, OK, and also ran schedmgr and scheduler416 with no luck. I reinstalled Acronis True Image Home 11. I tried building the backup in exactly the same folder with no other files present. The same error message occurs when running the incremental backup.