Just started today - went to remap weapons and game/console freezes. Tried clearing cache, deleted update, deleted non-essential game saves, deleted game and re-installed, tried different controller. Does the same thing when I try switching weapons using the D-pad. Randomly exhibits same problem when trying to enter VATS. I'm stumped, and can't locate a clue on this forum. I'm going to try XBOX Support next, but sure hope someone here knows how to solve this. I have tried loading a prior game save from a different playthrough and it works perfect. I have not downloaded the new HH dlc. Any help is greatly appreciated.
5/18/11 Don't know if this matters, but I was in the Camp McCarran Concourse area when it started. I had just finished fixing the food processor.

This is the exact glitch that forced me to abandon my last file. I had just left the Crimson Caravan and spoke with the robotic gun runner merchant. I modded a few weapons. After doing business with him the weapon switching crashes occurs. I have to assume it was from modding a certain weapon but who knows. Really hope they get their sh*t together and fix this game.

Now that you mention it, I might have done the same thing before going back to the concourse. I'm always hitting the different vendors looking for special ammo and upgrades. Needless to say, I had to abandon a level 31 player after 100+ hours of play and start over. If this is the way Bethesda and Obsidian want to treat their customers, then I will never spend another dime on their sub-standard and defective products. Too bad, because I thought Fallout 3 was a hoot, and rarely had a problem with it. Fallout: New Vegas crashes on my console every few hours of play - sometimes when loading my game save to continue playing. If it was up to me I would fire everyone in their Quality and Testing organizations and start fresh. I doubt they even care - they have our money. The only difference between them and Jesse James (the outlaw) - his gang used guns!!!