i've just found a way to solve it today frm mepis forum (so much to work today..
it sounds like:
put "blacklist nvidiafb" in it
cross your fingers
it should depend on the fact that new liquorix (not that sure though) stuff loads the nouveau drivers in the earliest booting stages, much earlier than x can call nvidia/nouveau/whatever
so far it's working
what pisses me off is some kernel panic at booting, though i noticed that with previous version of normal kernel it was less bothering, the only way to make machine start pretty safely now is to switch it off as i get the kernel panic, mere rebooting will just change message
odd thing is that once the machine starts i get no freezing nor any other issue