Comment 1 for bug 1179527

I don't have an immediate answer, but you might check for a file that is deleted out of a directory which is also deleted.
Or possibly the reverse, a directory which is deleted in the source branch, but has an extra file in the target branch.

The fact that file-id is None, indicates it thinks it is talking about an unversioned file.

You might also try doing "bzr clean-tree [--ignored]" to clear out any unversioned files.