Thanks for your responses all, I tried reinstalling DirectX, installing graphic card driver from nvidia website, i don't know what is DWM thought... but i have everything disabled through FFXIV Config (Ambient Occlusion, Depth of Field...), last i can do is install & patch from scratch but... ewww, i'll try that.

And at Seirra... well, my husband has the same graphic card than me, me on Win 7 he on Win XP, when he goes to Gridania his screen freezes for a sec then it changes all colors, shows loads of small horizontal lines in red/pink all the abilities and chat text become squares but it doesn't kick him out. Many people have problems in Gridania even with compatible cards.