A while ago I wanted to get back into Lost Odyssey and finish off the game.  When I put in the fourth disc, much to my dismay, gave me a unable to read disc message.  Which is odd because it isn't from my Xbox but from the game because it is able to partially load.  Also after close examination of the disc, there are no scratches.

I would like to pose a question to the community, "What can I do?"  I already invested 100+ hours into the game and want to finish it and find out how the interesting story turns out.  Is this glitch seen before and if so, how can it be fixed?  Do I need to bite the bullet and buy the game again (even though it's only the fourth disc that is the problem)?  Any help would be appreciated.