I am an impatient man!
Opened up the keyboard, saw that one of the switch's pin was not soldered very well (it was a bit higher than the pcb, as if it was levitating). Unsoldered, resoldered, everything works like a charm.
I'm off the warranty (destroyed that beautiful white OK sticker) but I was too lazy sending the keyboard back to Taiwan anyway
Hopefully no other problems will occur, or if they do occur they can be easily fixed
Thanx all for your assistance