Well, my laptop decided today was update day... and a big one it is. So catch you after the reboot

Update: extensions are broken, but are now updated.
And after some tweaking the the custom theme (i.e., setting it to 'default'), all seems the same as it was before.
Let's reboot again.
Update 2: all seems fine. Numix theme working like a charm (after an update from AUR).
So, thanks to all the Devs!