Sparks

My game worked perfectly since the day I bought it. Now it apears that anywhere there is writen text in my game it is replaced with random text. For instance when I talk to characters my reply options are not what they should be. they will something like the stats for a lightsaber or sonic grenade. The same goes for the subtitles when aliens speak or when I look in my journal. I have tried going back to previously saved games, starting new games, etc. Nothing seems to work. I even went as far as going out in a snow storm to get a new copy and still I have the same problem. I tried KOTOR 1 again and it works fine, so do my other games... The game is actually unplayable right now, I got understand people and I have no way of knowing what i'm going to say or do to other people.