Comment 5 for bug 1691865

For anyone coming across this same issue, the fix to get gvfs working was to add an entry "client use spnego = no" in the [global] section of the file /etc/samba/smb.conf. Without this line, gvfs can't authenticate properly on password-protected shares.

For further reference, I encountered three additional problems:

1. gvfs does not recognise hostnames, so I had to convert airport-time-capsule.local => 10.0.1.1

2. gvfs seems to convert share names to lowercase, so I had to change the target share from /Data to => /data

3. Deja-Dup wasn't happy about the backup directory that was there already (from the same machine). I had to delete this. It remains to be seen whether I will be able to backup again after this initial backup completes.