i've saw a lot of topic where summoners talk about this error, well long story short i've got this problem too, i've got a pretty old graphics card. a Radeon X1650 , i've tried to install latest directx version but nothing. i'm in your hands.. thanks

It's not something you can install, you need a new graphics card / computer.

i'm playing LoL since june. -.-

k, the problem is gone.. solved

@Spumeggiante

It would be most helpful for other people in your situation if you post what you did to correct the error:

i.e. Installing new gfx drivers, etc.

Always note also :
Before installing any new gfx driver, always UNINSTALL the previous one.
If not done, this alone can cause numerous hassles and headaches.