Comment 8 for bug 1270251

I had a similar problem, here's the output in apt-get upgrade:

dpkg: error processing /var/cache/apt/archives/shotwell_0.18.0-1~saucy1_i386.deb (--unpack):
 trying to overwrite '/usr/share/GConf/gsettings/shotwell.convert', which is also in package shotwell-common 0.15.0-0ubuntu1
No apport report written because MaxReports is reached already
dpkg-deb: error: subprocess paste was killed by signal (Broken pipe)

I uninstalled shotwell, autoremoved and reinstalled shotwell. everything if fine now.

sudo apt-get remove shotwell
sudo apt-get autoremove # This removed shotwell-common
sudo apt-get install shotwell

I have yorba's ppa configured:
deb http://ppa.launchpad.net/yorba/ppa/ubuntu saucy main

If I remember correctly I configured yorba's ppa to use shotwell under xubuntu after migrating my system from ubuntu.