Fallout is pretty buggy unfortunately. And the 360 version is said to be more stable than the PS3 one.
Companions randomly die on more than one occasion. Happened at the top of the Statesman Hotel when we weren't even under fire.
Encountered a Ghoul Reaver in the wasteland who was moving at 10 times normal speed and was glitching all over the place. Took nearly 5 minutes to kill and the body ended up floating upside down.
Operation Anchorage's elevator made Charon vanish out of the game, with my best power armor and a ton of loot. Went to an old save on that one, fired him, started the dlc, than exited to travel back to the Ghoul underground and wait for him to show up, which he did after a few days.
There also seems to be a glitch where a sniper rifle duplicates itself in Charons inventory perfect condition, but you can't actually remove the perfect rifle.
Maybe that's how companions actually use weapons and armor, by spawning a second set it peak condition, than despawning when not in use.