I wouldn't say he is a ghost against Barcelona because he cares more about his hair than anything else, or because he is disillusioned about some off-pitch stuff. In my honest opinion, this is because he can't handle the comparison that all media and all people around the world are making. When he was at United, it was alright because Messi wasn't yet the player he is today and back then they wasn't playing in the same league. Now they are in the same league and we can compare them each and every week (which we do). Furthermore, Messi is now a better player than him and I believe that when he (Ronaldo) is playing against Barça, he takes those games as an opportunity to prove the people he is the best player of them. Thus he is more concentrated in doing so than in doing the stuff he knows to do, and therefore he tries too hard and fails.. To my eyes, he has a Messi-complex.