did you install it to the HDD? Maybe that installed improperly and is causing problems. You could try reinstalling that.
If it's a disc with an error, a lot of companies will do a swap program. Call up Sega and see if they can offer you a cheap replacement. In the US it will typically cost you $5-10 for a replacement disc and you just have to send the money and the disc back to the company.
Or, if you feel like being a jerk to the next guy who buys it, there is the less honest way. Find a company with a stupid return policy (like EBGames) where you can buy a used game and return it no questions asked in the 1st week.








