That most likely is the problem. The BLUS code is region specific to your game disk. So it appears that the Nuketown code that you downloaded is for a different region and won't work on your game. Maybe someone with a better understanding of things could invalidate my arguement but I'm pretty sure that is what has happened here.
so then you live in europe? blus is from us . so it won't work
maybe try this
Firstly delete you black ops game data from the game data utility
Then go into your account management -> transaction management* -> Downloads list*
now you should see several different downloads for the nuketown map.You need to download the one that has the same BLES code as your disc.
if that doesnt work, gues you f****d