gui crash - Mint 12 gnome

[makyura]

i'm actually using mint 12 gnome 32bit on 2pc: one is a notebook (centrino 2 Ghz 1,2 GB ddr 333 of ram and a radeon mobility x600) and the other a desktop (phenom 9950 x4 black edition, 4GB ddr2 1033, radeon hd 4870) on each sistem almost every time the gnome gui crash especially when using world of warcraftand 2/3 of the desktop aren't usable; if i use gnome classic there is no problem at all so, what can i do to solve the problem?