LaTeX.org

The problem should be due to a system-update with backports activated in the sources.list.

There's a solution: https://bugs.launchpad.net/ubuntu/+source/lyx/+bug/228067 .
To put it in a nutshell:
1. Disable the backports updates (unsupported) in the update manager
2. apt-get remove libqt4-dbus ...