Oddball Graphics Glitch

[Zedmeister]

Ok I am getting a strange graphics glitch:

Basically during games of Half Life 2, Thief 3 and Farcry (Only noticed in these so far, others could also be glitching but I haven't noticed) I get certain graphic errors:
Half-Life 2 - The weapons disappear, or only partly display and flicker as I move about
Thief 3 - The lighting isn't displayed correctly, it'll flicker through floors and make an area look bright when it isn't
Far Cry - The ground doesn't display. As I am walking around the first level everything displays apart from the ground, so i look down and see the water flowing about. The odd corner might display and the land flickers.

The all sound different, but when experienced are very similar. Any help/advice appreciated.

Spec-ticulars:

OS - Microsoft Windows XP Pro
Graphics Card - Asus ATI Radeon AX800 XT 256MB DDR3
CPU - AMD Athlon 64 3500+ (S939)
Motherboard - Asus A8V Deluxe (Socket 939) Wireless Edition
Power Supply - OCZ PowerStream 520W
Memory - OCZ 1GB (2x512MB) PC3200 Dual Channel Platinum Edition
Sound Card - Creative Sound Blaster Audigy ZS Platinum Pro 7.1
Hard Drive - Maxtor DiamondMax 9 250Gb S-ATA
Running DirectX 9.0b

Everything is legit, bought and paid for.

[Ferral]

Make sure you are running the latest drivers (should imagine you have already done that) and remove any overclocking you may have setup.

Another one is update the bios on you're motherboard, this will make sure that you have fully compatible bios with everything else. I had to do this on mine, my board had version 1.0 bios and I was getting poor performance on the graphics and weird glitches on the graphics, weird blocks round sprites, blocks appearing onscreen after loading up a savegame in Farcry and a few other weird things on different games. I dont have the same vga card as you but it sounds like you are having the same probs as I had before the bios update.

[autopilot]

If your still getting it with the new drivers, also try disabling AI and fastwrites in the ATI CC/CP. Helped me anyway.

[Zedmeister]

Finally fixed it, thanks for the help Gents. I had to go all round the houses to get it sorted:

HL2 - Removed this ASUS Ati Enhanced driver (No idea why this was installed)
Far Cry - Still wasn't working, so I reinstalled (Again) the catalyst drivers
Thief 3 - With far cry working, this wasn't. Figured out I needed to install the Microsoft .NET framework (!?!?!?!) it now works. Oddball indeed!

Anyway, thanks again!