Comment 67 for bug 487720

In my case it turns out that two of the volumes were truncated somehow. Not sure if this is the sort of filesystem corruption that can occur when a removable volume is disconnected without unmounting it, but that would probably make sense.

Edited to remove incoherent ranting and raving while I was flailing around trying to save my data. See the comment below for a link to a bugfix to duplicity that enables a workaround, as well as a script to reproduce the problem.

The larger issue remains which is that deja-dup doesn't give you any way to recover from a corrupted volume, but that is a much harder UI problem.