Where are you exactly in the game? Did you passed the Leviathan?
This is a known glitch for the xbox. I think it happens with the galaxy droid glitch, which occurs most of the time after the Leviathan. If this is the case, I would go back to a save before you leave the Leviathan.
I am also moving this thread to the appropriate forum since it is xbox related.
The Work Bench = PC versions of KotOR and soon TSL
Ebon Hawk's Machine Room = xbox versions of KOtor and TSL
Prouver que j'ai raison serait accorder que je puis avoir tort. ~ Beaumarchais