Thank you for the reply Sub-Xero. I apologize for the delay in our response.

Do you have any part of your PC overclocked? If so, revert these to their standard clock speeds. Additionally, double-check that nothing is overheating on your PC.

If you have not tried it already, set the Windows compatibility to Windows 7. Right-click on the ffxivboot.exe file and select ‘Properties.’ Then select the ‘Compatibility’ tab and choose Windows 7.

You may also want to try a reinstall of the game. When you do, make sure to remove the locally-saved data folder (located My Documents > My Games > Final Fantasy XIV). Be sure to make a backup of this just in case it doesn't resolve the issue.

We hope we can be of assistance in helping you enjoy the exciting world of Final Fantasy XIV!