Fate crashes

[Kennitus]

So it's been like 2 weeks I've been playing and I've noticed that when I enter a Fate sometimes the game crashes, it really bothers me because it happens when I'm doing some Fate group too so I have to relog to the game and sometimes loose the Fate credits. Only once I've crashed in a town, Gridania near the Adventurer's Guild but it said "True functional issue" or some thing like that in a poped windows (not in the game), sometimes this message appears too when crashing while entering a Fate.
Did anyone have this issue too? How to fix it? I've already updated my graphic card driver, but it was happening too in the beta before I update, sometimes in the loading screens too and town.

I play on a 2009 Windows 7 64 bits with a XP boot inside. My graphic card is a Nvidia GT 440. And will it happen too when I'll upgrade it to the GTX 760?

Many thanks.