Jinwa, when you reinstalled Windows, did you make sure to delete all partitions and wipe them clean? Also, did you reinstall any other programs before FFXIV?

And GMs can't do much on this problem, it's Square Enix's Support that should do something. Yet they're kind of avoiding the issue, most likely because they got no idea on how to fix this.

If you see no conflicts between FFXIV and other applications, then it's most likely a flaw in one of the patches of the game. Just to be safe though, you could uninstall some undesired programs, run your antivirus program for a complete wipe of the virus, and then try again.