I had played for about 30 hours when the game started locking up every time I went into combat. I tried clearing the memory cache on my 360 and the game cache at startup, but nothing worked.

I started a new game to see if my saved games might be corrupted. The game didn't freeze when my new character went into combat.

So I reloaded one of my previous saves hoping that the new game had cleared the glitch, but the game still froze in combat. The game didn't always lock up immediately and it appeared to happen when my companions (Ed-E and Boone) joined the fight. So, I left my companions in New Vegas, went out to the wastes alone and attacked some Longhorns. The game did not freeze in combat. So I reloaded my save, left Boone and took Ed-E with me. Attacked the Longhorns with Ed-E and the game did not freeze in combat.

Reloaded my save, left Ed-E and took Boone. Attacked the Longhorns with Boone and the game froze. It appeared to freeze as soon as Boone started firing.

Again I reloaded one of my previous saves that been freezing in combat (actually when I first encountered the combat freezes). I left Boone far enough away not to be involved and started combat. The game did not freeze.

I wondered if it was because of the weapons I had given to Boone, so I stripped him of all his weapons so that he could only use his sniper rifle. Took Ed-E and Boone into combat and the game didn't freeze. It appears that one of the Laser rifles I had given Boone to use was causing the game to freeze in combat.

The game still has some other combat glitches that seem to relate to Boone, but don't cause the game to crash or freeze. Most noticeably, the game slows down if Boone kills the last enemy in combat.

I haven't started experimenting yet to see what weapons are safe to use and what might cause the game to crash. If i can nail it down, I'll repost. Hope this helps!