Comment 16 for bug 614993

The problem is that the package "xserver-xorg-video-v4l" is demoted from main to universe. Apt will try to find a solution for the xserver problem by upgrading to the latest xserver abi (because of the breaks). But it can't find one because there is no newer version of xserver-xorg-video-v4l available.

The best fix I can think of currently is a explict:

Package: xserver-xorg-core
Conflicts: xserver-xorg-video-v4l (<< 1:0.2.0-4ubuntu1)

to ensure the upgrade works. I'm testing this now.