This is a regression in the client program I am very sure. I won't get it last week and now I get it every time I am in the game playing and alt-tabbed.
My computer configuration stayed the same (that computer I only use it for FF14 and FF14 forum bowsing. I do my other works on my other 5 computers), no windows upgrade or whatnot.

Interesting thing is it never happens on title screen/character selection screen.