Duke of Nukes

so I played the first time through and everything worked more or less flawlessly, just a few of the minor glitches that dont stop the game or anything. When I started the second time through though, I noticed I could no longer open my old save games (game 1 and game 2). I went away for a week, and my roommate started a new game in my absense, and now the only saves are from his game, but they still show up as Game 5 and Game 6. So it would seem that although the games are saved, something about starting a new game makes it impossible to load the saves from any older games....is there a way to fix this?