I'm afraid I have no idea why this might have broken. I'm no expert on this desktop type stuff. Personally I use xtrlock as my screenlocker.
It is possible that this is related to the cgroups fs problem for which Michael Biebl applied a patch, and which I have uploaded to Debian experimental. You could try systemd-shim 10-3~exp2. If you find out what the problem is, I would apply a patch to systemd-shim (if applicable). Good luck. Ian. -- Ian Jackson <ijack...@chiark.greenend.org.uk> These opinions are my own. If I emailed you from an address @fyvzl.net or @evade.org.uk, that is a private address which bypasses my fierce spamfilter.