If you have any video-capture software (eg OBS, nVidia Experience, AMD Raptr, MSI Afterburner) Make sure only ONE of these is running, and make sure the rest are closed before launching FFXIV.

In the case of nVidia Experience and AMD Raptr, these will crash the game if they are closed while the game runs. In the case of MSI Afterburner, Afterburner will usually just crash and remain crashed. Other software like Fraps and OBS may also do this.

The only way I've ever been able to get the game client to crash without the video capture software being the culprit is if the video driver resets (caused by the the video card malfunctioning) So that's also a possibility.