Not Square-Enix support, but I would check the Windows event log. (Windows menu, type 'Event', pick 'Event Viewer', open the 'Windows Logs' folder, and check 'System'. It might also be worth checking under Applications and Services Logs, and looking at Hardware Events.)

Either way, if something's going wrong at a system level, it's unlikely FFXIV is the root cause; it may be the trigger that touches off some other system issue (and based on what you say, probably is), but if it's happening to your system overall -- including, it seems, the USB bus shutting down (such that your mouse and keyboard LEDs go poof) -- it's almost got to be something at a deeper level that's the actual underlying issue.

(Like an allergy; the underlying problem is the allergy, but FFXIV is the allergen that causes the allergic reaction. If that makes sense.)