The World War Hulk tie in issues threw their whole schedule off, so I'm willing to bet that Chaos has the right idea.
Well, their schedule should have been set up a long time ago by the editor, so that's really Tom Brevoort's fault, if anybody. And it goes all the way back to the lateness of the Ellis/Granov issues, since that threw the whole shebang off from the get-go. That's why IM's Civil War tie-in issues were so near the end of the event, because the Knaufs were already months behind thanks to Granov taking too long. Compound it with the WWH tie-in issues, and yeah, it's a mess...