Yeah right, Umnir ! Perkele !
I received my new graphic card, I sent the other because I thought it was broken and it appears I was right. I can now play Painkiller, Fear and Quake 4 (as far as I know...

).
ATI drivers are horrible really.
The newest version is the 10.7.
Formerly I had the 10.4.
All games I tried runned well.
I knew that 10.5 and 10.6 versions fuck up Quake Live colors so I didn't even install it (it works perfectly with 10.4 !!!, later release, bug...).
I tried the 10.7 then because I heard the Quake Live problems were solved.
INDEED, the colors were okay.
But then : Quake 2 -> impossible to play in OpenGl mode -> with 10.4 100% fine.
Quake 4 -> Ultra sloppy mouse, crosshair doesn't even move if I move my mouse too slowly -> with 10.4 100% fine.
So I went back to 10.4 pffff.
I can't understand what they are doing with drivers updates, isn't it supposed to solve problems instead of adding other ?
Anyway I lost lots of times trying to get my new PC to run fine. I also had a pain finding a way to increase the sample rate of my USB port for my mouse so that I put it to 500Hz frequency instead of 125Hz (default setting, with more input lag).
I'm going back to mapedit as soon as I have installed OUWB + DosBox and when Quake 2 + addons and Quake 4 singleplayers are finished.
I'm currently going through the end of my Quake 2 adventures. I'll post some thought about it when it's done.
Um, so that was the explanation as to my absence these days.
I hope you all do well. Don't forget I'm a dick when it comes to mapedit so I might have shitloads of question to ask in a near future.