LOL
PROBLEM SOLVED!
So here is what was actually causing the problem: a stupid ‘update’ that ThemeForest made me buy for 5 $
– there is a thread about this issue in the forum in fact –
for a theme that is omonymous ‘origami’ by another designer
I had the feeling that theme was messing up with ‘our’ Origami and indeed it was: once I deleted the theme from the WP manager,
the error instantly disappeared!
Forum manager: spread the word! Also to these guys at ThemeForest (who could refund us these 5 bucks for a suggested update that not only is not for the right theme but it also screws up the one we bought..)
Thanks Akullander !
I feel almost like a geek girl now!