I can confirm the problem with smb backend. Here's my log output:

$ DEJA_DUP_DEBUG=1 deja-dup --backup
DUPLICITY: INFO 1
DUPLICITY: . Using archive dir: /home/tom/.cache/deja-dup/c29ce7486bdf2672249a6257f783d051

DUPLICITY: INFO 1
DUPLICITY: . Using backup name: c29ce7486bdf2672249a6257f783d051

DUPLICITY: INFO 1
DUPLICITY: . Import of duplicity.backends.ftpsbackend Succeeded

DUPLICITY: INFO 1
DUPLICITY: . Import of duplicity.backends.rsyncbackend Succeeded

DUPLICITY: INFO 1
DUPLICITY: . Import of duplicity.backends.u1backend Succeeded

DUPLICITY: INFO 1
DUPLICITY: . Import of duplicity.backends.webdavbackend Succeeded

DUPLICITY: INFO 1
DUPLICITY: . Import of duplicity.backends.cloudfilesbackend Succeeded

DUPLICITY: INFO 1
DUPLICITY: . Import of duplicity.backends.ftpbackend Succeeded

DUPLICITY: INFO 1
DUPLICITY: . Import of duplicity.backends.tahoebackend Succeeded

DUPLICITY: INFO 1
DUPLICITY: . Import of duplicity.backends.hsibackend Succeeded

DUPLICITY: INFO 1
DUPLICITY: . Import of duplicity.backends.gdocsbackend Succeeded

DUPLICITY: INFO 1
DUPLICITY: . Import of duplicity.backends.imapbackend Succeeded

DUPLICITY: INFO 1
DUPLICITY: . Import of duplicity.backends.sshbackend Succeeded

DUPLICITY: INFO 1
DUPLICITY: . Import of duplicity.backends.botobackend Succeeded

DUPLICITY: INFO 1
DUPLICITY: . Import of duplicity.backends.localbackend Succeeded

DUPLICITY: INFO 1
DUPLICITY: . Main action: collection-status

DUPLICITY: INFO 1
DUPLICITY: . ================================================================================

DUPLICITY: INFO 1
DUPLICITY: . duplicity 0.6.20 (October 28, 2012)

DUPLICITY: INFO 1
DUPLICITY: . Args: /usr/bin/duplicity collection-status --include=/home/tom/Software --include=/home/tom/Music --include=/home/tom/env --include=/home/tom/Pictures --include=/home/tom/Documents --exclude=/home/tom/.cache/thumbnails --exclude=/home/tom/Downloads --exclude=/home/tom/.local/share/Trash --exclude=/sys --exclude=/proc --exclude=/tmp --exclude=/home/tom/.xsession-errors --exclude=/home/tom/.thumbnails --exclude=/home/tom/.gvfs --exclude=/home/tom/.adobe/Flash_Player/AssetCache --exclude=/home/tom/.cache/deja-dup --exclude=/home/tom/.cache --exclude=** --gio smb://fritz.box/mass-storagedevice-01/tom --no-encryption --verbosity=9 --gpg-options=--no-use-agent --archive-dir=/home/tom/.cache/deja-dup --log-fd=17

DUPLICITY: INFO 1
DUPLICITY: . Linux avocado 3.8-trunk-amd64 #1 SMP Debian 3.8.5-1~experimental.1 x86_64 

DUPLICITY: INFO 1
DUPLICITY: . /usr/bin/python 2.7.4 (default, Apr 10 2013, 23:24:08) 
DUPLICITY: . [GCC 4.7.2]

DUPLICITY: INFO 1
DUPLICITY: . ================================================================================

DUPLICITY: NOTICE 1
DUPLICITY: . Local and Remote metadata are synchronized, no sync needed.

DUPLICITY: WARNING 1
DUPLICITY: . Attempt 1 failed: Error: Invalid argument

DUPLICITY: DEBUG 1
DUPLICITY: . Backtrace of previous error: Traceback (innermost last):
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backend.py", line 316, in iterate
DUPLICITY: .     return fn(*args, **kwargs)
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backends/giobackend.py", line 160, in list
DUPLICITY: .     self.remote_file.get_parse_name())
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backends/giobackend.py", line 106, in handle_error
DUPLICITY: .     raise e
DUPLICITY: .  Error: Invalid argument
DUPLICITY: . 

DUPLICITY: WARNING 1
DUPLICITY: . Attempt 2 failed: Error: Invalid argument

DUPLICITY: DEBUG 1
DUPLICITY: . Backtrace of previous error: Traceback (innermost last):
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backend.py", line 316, in iterate
DUPLICITY: .     return fn(*args, **kwargs)
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backends/giobackend.py", line 160, in list
DUPLICITY: .     self.remote_file.get_parse_name())
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backends/giobackend.py", line 106, in handle_error
DUPLICITY: .     raise e
DUPLICITY: .  Error: Invalid argument
DUPLICITY: . 

DUPLICITY: WARNING 1
DUPLICITY: . Attempt 3 failed: Error: Invalid argument

DUPLICITY: DEBUG 1
DUPLICITY: . Backtrace of previous error: Traceback (innermost last):
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backend.py", line 316, in iterate
DUPLICITY: .     return fn(*args, **kwargs)
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backends/giobackend.py", line 160, in list
DUPLICITY: .     self.remote_file.get_parse_name())
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backends/giobackend.py", line 106, in handle_error
DUPLICITY: .     raise e
DUPLICITY: .  Error: Invalid argument
DUPLICITY: . 

DUPLICITY: WARNING 1
DUPLICITY: . Attempt 4 failed: Error: Invalid argument

DUPLICITY: DEBUG 1
DUPLICITY: . Backtrace of previous error: Traceback (innermost last):
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backend.py", line 316, in iterate
DUPLICITY: .     return fn(*args, **kwargs)
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backends/giobackend.py", line 160, in list
DUPLICITY: .     self.remote_file.get_parse_name())
DUPLICITY: .   File "/usr/lib/python2.7/dist-packages/duplicity/backends/giobackend.py", line 106, in handle_error
DUPLICITY: .     raise e
DUPLICITY: .  Error: Invalid argument
DUPLICITY: . 

DUPLICITY: ERROR 50 list 'smb://fritz.box/mass-storagedevice-01/tom'
DUPLICITY: . Invalid argument

DUPLICITY: INFO 1
DUPLICITY: . Using temporary directory /tmp/duplicity-Cn4g7S-tempdir