Sounds like the saved tournament was corrupted. Possibly the system forced the TD application to exit while writing out the tournament file. Or something.
Likely not something that can be fixed, but if you send me the saved tournament file I can look at it. Send it to support@thetournamentdirector.net.
Consider turning on the backup feature: Preferences tab -> Loading / Saving category -> Make backups when saving tournaments
At least this way you might have a previously saved version of the tournament. It might not have all the latest changes that happened in the tournament, but that might be easier to fix than a corrupted tournament file.