If you go from the main screen to Game Settings -> Troubleshooting -> Open folder containing saved games, you should see a bunch of folders like "mygame.lg". Inside each of them there are a bunch of other folders.
The first thing to check is if it's a flaw with your core game files. I'd suggest creating a new folder (call it something like test.lg), then from your saved game, copy all the .dat files into that new folder (there are 15-17 of them or so). Then try to open this test game. If you still have troubles, please follow the instructions to send us your files (
How to FTP files to OOTP Developments - Powered by Kayako Help Desk Software), and we can see if there's something in your game itself causing problems.
If that does work, then I would suggest going through your main league and as Spritze mentioned, clean up certain files that are not needed. It's possible there's a corrupt image file, for example, which could cause problems. Sometimes there's a file that Windows somehow still holds a file lock on, so our game can't load them (I've seen them with player histories, for example). Even simply copying your entire folder to a new folder and using that instead can fix problems.