Comment 14 for bug 1722454

Please upgrade to the current version of duplicity, 0.7.16. This will assure that any bugs fixed since your release are available and may fix your issue. This applies especially to duplicity versions between 0.7.03 and 0.7.14 inclusive. There was a fix in 0.7.15 that reduced memory usage drastically, and will help with memory errors and inability to start new threads.
The bug that was resolved in 0.7.15:

* Fixed bug #1720159 - Cannot allocate memory with large manifest file since 0.7.03
  - filelist is not read if --file-changed option in collection-status not present
  - This will keep memory usage lower in non collection-status operations

There are three options:
* Release tarball Install - https://launchpad.net/duplicity/+download
* Daily duplicity builds - https://launchpad.net/~duplicity-team/+archive/ubuntu/daily
* Stable duplicity builds - https://launchpad.net/~duplicity-team/+archive/ubuntu/ppa

NOTE: UNinstall duplicity first if it was installed via the distribution repository. For Ubuntu, that would be "sudo apt-get purge duplicity".