Melo really failed his team at the end there. They needed a big 4th quarter from him (and Billups) and neither of them were particularly great - though at least Billups kept his team in it for the most part, aside from that idiotic 3 from a few feet behind the arc at the end of the game.
As much as some here might hate to admit it, Kobe showed how great of a closer he is at the end of Game 3. Melo and Billups couldn't match it, and the Nuggets lost.
Not to mention all those stupid 3s the Nuggets chucked up earlier in the game which prevented them from building a greater lead. Oh, and the fact that they can't make decent in bounds passes at the end of games.