I was in the middle of the main story quest... I'll put a spoiler label just so I won't spoil anything for anyone who hasn't played it.
[spoiler]It in the quest where I have to help my father with Project Purity, at the point where the Enclave shows up to steal the project. After the guy killed one of the scientists and my kills them with a high does of radiation. At this point, I am suppose to follow Dr. Li out of the Jefferson Memorial. But this is where I have a problem: the moment I walk out the door, the game freezes during loading. I tried pressing the Xbox dashboard button to see it was taking a long time to load; turns out the game crushes at this point.[/spoiler]
Long story short, the game f*cks up during loading when I enter the next room to continue in my quest. I dunno if it has to do with the disc being scratched up, because my brother borrowed from a friend of his who has a 360, and the disc is really scratched up, though it seems to be a very likely case. But all I know is that I am (probably) not going to waste another 20+ hours to get back where I was when the game began to f*ck up out of sheer frustration.