It's a bog standard memory access denied error. The information you provided is too vague. Check for malware. Check for viruses. Reinstall FFXIV. Reinstall graphics drivers. Reinstall chipset drivers. Run Windows Update. Run a memory test. Reinstall OS. Replace your RAM. Replace your Hard Drive. Replace your CPU. Replace your motherboard. Replace your GPU. Any or all of these could possibly fix it. The cause is of the error could be anything. Did you look in your event viewer? Did you test other games? Did you test DirectX? Did you run chkdisk? Did you recently update?