Word from the set of The Incredible Hulk is that there is tension between Marvel Studios and Edward Norton, who was promised a measure of creative control for his participation in the project. See, Norton doesn't like the cut of the film the way that Marvel's doing it, and is sort of threatening to remove his support from the project unless they let him supervise the next cut.
Now, for a franchise that's already had to hit reset, due to the fact that it didn't work so well the first time, the withdrawal of support from the lead actor would spell disaster, and potentially put at risk over $100 million in cost, plus whatever goodwill and marketing the film has in the hopper. In other words, Norton has them over a barrel...and you wouldn't like him when he's angry.
In the meantime, you should watch the teaser trailer for the film, which is great.
Deadline Hollywood Daily: Ed Norton And Marvel In 'Hulk'-ing Feud