Comment 10 for bug 1272720

Addendum:

Booting the previous 3.13.0-6-generic will continue to boot but shows the "firmwre not responding" error briefly.
The update that triggered the regression was:

Start-Date: 2014-02-06 11:56:33
Commandline: apt-get -y upgrade
Upgrade: libdpkg-perl:i386 (1.17.5ubuntu2, 1.17.5ubuntu3), libfontembed1:i386 (1.0.44-1, 1.0.44-2), abiword-common:i386 (3.0.0-2ubuntu1, 3.0.0-4), ubuntu-standard:i386 (1.315, 1.316), dpkg:i386 (1.17.5ubuntu2, 1.17.5ubuntu3), libcupsfilters1:i386 (1.0.44-1, 1.0.44-2), libabiword-3.0:i386 (3.0.0-2ubuntu1, 3.0.0-4), libgirepository-1.0-1:i386 (1.39.3-0ubuntu1, 1.39.3-0ubuntu2), dpkg-dev:i386 (1.17.5ubuntu2, 1.17.5ubuntu3), libevview3-3:i386 (3.10.3-0ubuntu2, 3.10.3-0ubuntu3), gir1.2-freedesktop:i386 (1.39.3-0ubuntu1, 1.39.3-0ubuntu2), xserver-common:i386 (1.15.0-1ubuntu1, 1.15.0-1ubuntu2), cups-filters:i386 (1.0.44-1, 1.0.44-2), linux-libc-dev:i386 (3.13.0-7.25, 3.13.0-7.26), xserver-xorg-video-intel:i386 (2.99.907-0ubuntu2, 2.99.909-0ubuntu2), evince-common:i386 (3.10.3-0ubuntu2, 3.10.3-0ubuntu3), abiword:i386 (3.0.0-2ubuntu1, 3.0.0-4), gir1.2-glib-2.0:i386 (1.39.3-0ubuntu1, 1.39.3-0ubuntu2), linux-image-extra-3.13.0-7-generic:i386 (3.13.0-7.25, 3.13.0-7.26), linux-image-3.13.0-7-generic:i386 (3.13.0-7.25, 3.13.0-7.26), dh-python:i386 (1.20131021-1ubuntu8, 1.20140128-1ubuntu1), ubuntu-minimal:i386 (1.315, 1.316), evince:i386 (3.10.3-0ubuntu2, 3.10.3-0ubuntu3), libevdocument3-4:i386 (3.10.3-0ubuntu2, 3.10.3-0ubuntu3), cups-filters-core-drivers:i386 (1.0.44-1, 1.0.44-2)
End-Date: 2014-02-06 11:59:37

During upgrade this warning appeared twice:

dkms: WARNING: Linux headers are missing, which may explain the above failures.
      please install the linux-headers-3.13.0-7-generic package to fix this.

Even though there were no further failures in the log I installed linux-headers-3.13.0-7-generic manually afterwards.