I remember that being an unfortunate problem that was encountered from time to time. Unless you have a recent backup of the save that's working, you don't have a lot of options except to leave that save behind and start over.
However, if you want to try and troubleshoot/restore it, RED MC is completely free and fully functional these days (and available
https://forums.nba-live.com/downloads.php?view=detail&df_id=8757 in our Downloads section). You could try starting a new save and copying the data from the old one to the new file, and see if that can be loaded. The basic steps would be as follows:
1. Run NBA 2K14.
2. Start a new Association game and save it.
3. Exit NBA 2K14.
4. Download and install RED MC. Note that you may have to disable your anti-virus software while you do this, as it can trigger false positives.
5. In RED MC, open up your original Association file (the one that isn't loading).
6. Choose the Export to CSV option from the File menu, and export the data to a CSV file. Make sure that you select the "Whole File" option so that all the data is exported.
7. Open up the new Association file (the one you've just created).
8. Choose the Import from CSV option from the File menu, and import the data from the CSV file you created in the previous step. Again, make sure that you select the "Whole File" option so that all the data is imported.
9. Save the changes to the Association file you just imported data into, and close the file/RED MC.
10. Run NBA 2K14, and try loading the new Association file.
No guarantees it will work, but that's how you'd get data from one Association file into another, and possibly work around the corruption. There's also no guarantees that the error won't happen again, but again, it's worth a try if you'd like to take a shot at getting the Association file back up and running.