ATI radeon 7000 problems

[JNGU]

Hi.. I recently bought a ATI radeon 7000 (only to play ffxi) and after playing for 5-10mins my screen gets blurry and scrambled at that time my ffxi becomes unplayable cause I can't see anything

I've done the following:
Reformated comp
Uninstalled and installed drivers (off cd)
Uninstalled an installed drivers (off some site on box)

anyways i'm running on
1.3ghz
516mb ram
ati radeon 7000

nothing great but i should be able to play ffxi

any advice would help i've had ffxi for 2 weeks now and i'm level 4.. thats just hurting