It tells you that your file is corrupted. You can then restore from backups, re-download, or take some other corrective action, such as delete the file, reboot

It tells you that your file is corrupted. You can then restore from backups, re-download, or take some other corrective action, such as delete the file, reboot the machine, re-install the operating system, or play Quake 2 to test your RAM and graphics. Never underestimate the value of a reason to play Quake 2.