If there is a minor scratch you might want to think about taking it to a place that resurfaces game discs. I had the same problem with a game I bought on Ebay and took it to Game X-change here to have it resurfaced and haven't had a problem with it since. Here's a place in Topeka that will do it for $3 it says:
http://www.cdtradepost.com/about-us.aspx