OK, i solved the problem by using another disc, however now i have another problem. Im near the end when you go back to Citadel Station(after landing at the jedi academy and defeating atris).
Whenever i try to go to residential modual 082 east the loading screen hangs. It will load maybe 2%, just enough to get to the point where it displays the second tip, then it doesnt load anymore. Ive let it sit there for quite a long time and nothing happens.