There was only one time out of about 150 of vanilla Oblivion on the 360 where I almost had a game breaking bug.
I forget the exact quest, but you had to talk to a statue or something and it would break because you didn't get an item, or it wouldn't register you had it or something like that.
The fix was hilarious convoluted. I remember you had to teleport to a specific city, walk backwards a few steps, and then exit the city gate or something crazy like that.
Anybody remember that one?
Maybe I have better luck than most people, but I don't have as much trouble as some do with Bethesda games. Fallout 3 froze a few times, but there wasn't anything game breaking. Once I loaded my save and all my items were removed and scattered around me in a circle, but it turned out it was my roommate messing with me. Took forever to pick all my lock picks back up. lol