This issue always re-occurs. Yet, I still haven't found out the best solutions. What works, is to link the Italian layout with the US layout:
% cd /System/Library/Keyboards
% mv USA.keymapping USA.keymapping.bak
% ln -s Italiano.keymapping USA.keymapping
It is not really a solution, rather a workaround. You'll find better ways to do this on a local Italian/European board/list, since they all share this problem with you.