The problem comes down to simple question "Is the software at fault or is the data file at fault?"?
If the data file is at fault, make a copy of the most recent data file. (This can be done by right-clicking and dragging the file's icon, and selecting Copy.) Now restore the COPY of the backup file. Did the problem go away? If so, create an emergency gedcom file. If not, do the same thing with the most recent previous backup, and then the next most recent, until you get to one that was created before the problem occurred. So the problem should be solved.
If this doesn't solve the problem after restoring the 5 most recent backups, it is probably the software that has become damaged. Download a fresh copy of the installer (from the website listed in the AFT forum) if you don't already have a saved copy of the installer. Uninstall the AFT software, if you can find it in Control Panel > Add/Remove Programs. If it isn't listed there, don't worry, just install AFT again. Now use the NEW copy of the AFT software to open the current AFT database.
Or email me a copy of your file. I have installed AFT temporarily on my flash drive, and should be able to open your AFT database and create a gedcom file for your use.
AFT is very old software (no longer available at ancestry.com) and there are better products available for free, including PAF5 at www.familysearch.org and Legacy6 at www.legacyfamilytree.com Either one will import a gedcom file created by AFT.