Comment 15 for bug 844369

I had exactly the same problem. I believe the problem stems from having the deja-dup folder in a subdirectory as the error being thrown out was:

UDFs can not be nested.

following taken from :http://askubuntu.com/questions/21621/ubuntu-one-wont-synchronize-pictures-folder
"...If you try to create a synchronized folder from something that is not an actual directory inside your home (if it is, for example, a symlink to somewhere else), or if it is a subdirectory of a synchronized folder, then the creation will fail.
If you try to do the same thing from the Terminal, you should get a slightly more verbose error message..."

"....(UDFs is what we Ubuntu One developers call synchronized folders)..."

 for me, running u1sdtool --list-folders displays
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kaipee@zoostorm-ubuntu:~$ u1sdtool --list-folders
Folder list:
  id=0875288d-04d3-4d5d-8fd4-79142504bd1e subscribed=False path=/home/kaipee/deja-dup/zoostorm-ubuntu
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In order to fix this I changed the deja-dup settings to "Backup location: Ubuntu One" - "Folder: zoostorm-ubuntu"
(ie removing the 'deja-dup/' part, so zoostorm-ubuntu folder is not a subdirectory of anything)

Just tried it and now my machine is currently backing up to Ubuntu One as I type this