dinkygreg

I am replaying Tomb Raider: Underworld again on my Xbox 360. Everything was alright until I reach Midgar serpent in Mexico where you need to find the four artifacts to open the circle-like gate to enter. The problem is that it doesn't save the current position at all. The game saved position normally after I reached Xibalba, but now it doesn't work. Can anyone help me to fix the glitch? Thanks..