duplicity crashed with ValueError in port()

You need to quote the target, at least, because it contains a space: 'ssh://User Name@localhost:/home/username/Backup' - or has this been cleaned by apport during report?

Anyway, the bug is still valid, because it should not crash, but report a sane error, if the port cannot get parsed. (I've looked not at the source code yet), but it looks like it parsed the URL wrong:
    File "/usr/lib/python2.5/site-packages/duplicity/urlparse_2_5.py", line 116, in port
      return int(port, 10)
  ValueError: invalid literal for int() with base 10: ''

I know I'm chiming in pretty late here, but this error is not due to spaces. It's because the user entered the target location using a colon at the end of the hostname (which is standard ssh syntax, but not for duplicity according to the man page). Instead of specifying the target as user@localhost:/path/to/backup, one should use user@localhost/path/to/backup. Apparently duplicity interprets the colon to mean that a port number follows. Clearly untrue. The issue of whether a sane error message should be printed still stands.

This fix was released in 0.5.10.

Karmic has 0.5.18