Why is Edward Norton not promoting the new Hulk movie?

Interesting stuff!
Fox:
Friday's premiere of "The Incredible Hulk" should prove big box office numbers, but not with any help from star Edward Norton.
Norton, I'm told, has slipped off to a desert island rather than do publicity for the movie he stars in and nominally wrote.
I say nominally because there's been a dispute right along about who did what on "Hulk." The screenplay is credited to "X-Men 3" writer Zak Penn, who definitely wrote the original draft and mapped out the movie.
But wasn't it only last July 2007 that Norton boasted of writing the screenplay at Comic-Con, the convention for people who trade comic books and associated materials? Uh, yes, he did.
I'm told that Norton did substantially rewrite the Penn draft, added lots of dialogue, and worked on the character of the Hulk's alter ego Bruce Banner to make him more human.
But Norton fell out with Marvel and Universal and declined to do much publicity. This left the bulk of it to co-star Liv Tyler.
Interestingly, Norton is not signed to do the typical two sequels to this "Hulk," although Tyler is and so, I'm told, is director Louis Leterrier. The reason for Norton holding out is likely a money issue. Could he be replaced in future versions? Undoubtedly, although that would be a shame. He's terrific as the un-jolly green giant.
Meantime, some Web sites like Cinematical have noted that Universal is using Robert Downey Jr.'s surprise appearance in "Hulk" as Tony Stark aka Iron Man in their TV commercials. Downey's presence was supposed to be a big twist at the end -- so much so that I kept it out of my review the other day. But I guess that Marvel and Universal want to capitalize on "Iron Man"'s huge box office.
So then the question is, will the "Iron Man" and "Hulk" sequels include a crossover by each character? Only Stan Lee knows the answer to that one.