Running in safe mode I could see an error message prompting me to run systemd which in turn showed that systemd-logger.service failed with code 218.
Browsing online and finding this page
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=628081 gave me the idea to try booting on another kernel.
(During a rescue attempt a few month back I added that kernel but went back to booting on my old when that was not the cause of the problem)