Ugh. Ran into problems with rdiff-backup — it fails trying to remove files (which it added perfectly well) which are over some length limit.
Have decided that rdiff-backup in Windows (probably mirrors in general, too) is just a bad idea: it’s too flaky, and when it fails it leaves your repository in an unrecoverable state. Better to backup to a single archive file I suppose, at least it won’t get corrupted. Will check out dar and duplicity instead.