The Microsoft Operations team has posted
a message to their blog about what happened with the Modern Warfare 2
DLC that went out yesterday. Here's the gist of what happened:
Through a process failure on our part, the Modern Warfare 2 Stimulus Package was released this morning before the Title Update (TU) for MW2 was available.
Unfortunately, the Stimulus Package doesn’t function correctly without the TU. Once they had been released out of order, it wasn’t a simple thing for us to resolve. For a couple of hours the result was unpredictable but most people couldn’t get into a game through matchmaking. In technical terms, it was a big hairball that we had to unwind.
From what I can tell it looks like almost all the problems have been solved so it's safe to go online and pick up the DLC now if you're so inclined. I'd mention that for the same 1200 points you'll be able to pick up Breach
in a few months (and support a cool indie developer) but I'm not that guy.