Weird FFXI graphics problemsFollow

I'm running FFXI on a Windows XP system with a GeForce FX 5600 256mb card (Asylum). Since upgrading to DirectX 9.0c I've been getting weird graphical glitches while casting spells or summoning Avatars, the effects are filled with little geometric "holes" and lines which get worse if other textured objects are visible behind them.

Lines on Ramuh - http://www.animespoiler.com/problem1.jpg

Shapes on Ramuh - http://www.animespoiler.com/problem2.jpg

I tried updating to the latest nVidia drivers and it didn't fix it. Downgrading to the WHQL signed nVidia drivers off the Windows Update site made the game either gradually turn every non-character texture gray or the game would start to seriously stutter, the music would skip and the mouse would only move in short spurts a few minutes after logging in. This last part affected the PlayOnline viewer as well as the game itself.

So I've switched back to the latest nVidia drivers, but it won't let me switch back to DirectX 9.0b since when I try it tells me that I've already got a newer version and I can't find a way to uninstall it. What's causing this? Can I fix it?

I was contacted by Square tech support, they recommended downgrading to nVidia driver 56.64 (which the email said it's the latest version of the drivers they support,) turning off Bump Mapping in the FFXI configuration utility and on turning on Fog Emulation in my video card's settings. Downgrading to 56.64 made it so that I couldn't get into windows at all until I went into safe mode, took out all traces of nVidia with Detonator RIP and then installed 56.64 clean from there, but doing that and turning off bump mapping seemed to do the trick. I couldn't find a setting for Fog Emulation. Now the game doesn't look as pretty as before and long-distance textures are grainy again, though, so I hope they fix the compatibility issue soon :(

It affected all Avatars, even the little neon rat.