I just had the same error.
- My backup was working great. It included a lot of directories, including “C:\user” and all subdirectories.
- I deleted some source files from the backup set (via the ‘edit’ option). Specifically, I deleted a cache directory from deep within the windows c:\USER…\appdata\mozilla… tree (as it was just continually backing up new cache files pointlessly)
- On the very next (and every subsequent) backup, I get the above error.
- I tried editing the job again, and the strange part is that the changes I made to the directory selections didn’t seem to ‘stick’. Deleting the whole C:\user directory didn’t help, and adding it back didn’t help either.
It may be pure co-incidence, but my gut tells me that deleting directories from the source list is related to the error.