While we were mostly happy to hear about a new patch for Fallout: New Vegas, turns out the update has created unexpected issues for many Xbox 360 owners -- specifically the "missing content" error.
If you've been afflicted by this issue, a post on the official Bethesda forums may provide some light at the end of your Fallout tunnel. A fix (an update for the update, if you will) is on its way, at least for the English version. The new update is expected to go live some time this evening, though no exact time was given. For anyone running the game in other languages, the wait will be longer.
There is a workaround to the problem that you may try in the mean time:
"For now, if your game save is working properly after getting the 'missing content' notice, here's what we suggest. Load your game save after getting the message about missing content. Once you're in the game, make a new game save, and moving forward you shouldn't have any issues. Once the new title update is up, you can then go back to your older save files."
Should your game still crash after, all you can really do is wait for the update.