It's a no brainer that the film is presumably violent, but it apparently included a scene depicting a shoot out in a movie theater.
Had it not been for the tragic event that unfolded in Aurora, Colorado last Friday, viewers probably wouldn't have batted an eye during the sequence. However, the world has reacted to James Holmes' horrible shooting spree and no one really wants to be reminded of his actions.
The plan is to reshoot some scenes to make the movie work and then (tentatively) release it on January 11, 2013. The only obstacle standing in the studio's way is reassembling the ginormous cast of A-listers who are probably busy shooting other projects.
Whatever the case, good luck!