I have recently install Mageia 2 KDE4 from live usb and I was having two issues even after installing nvidia's proprietary graphics from the repo.
Firstly, the bootscreen/splash is laggy as hell, for passing from a image to the next one( I mean for seen one bubble and after two, I have a black screen and the next image is appearing from up to down in slow motion lol
Secondly, I have a lot of black dots/pixels in the upper left screen. And no, they're not dead pixel, I don't have it in the splash/bootscreen either in windows.
Both of problems are seen with the nouveau driver and the proprietory one.
http://i.imgur.com/PG7zC.png
Sorry for my not perfect English and thanks for taking your time for me

Edit 1: The second one seem to be solved by only changing the tty and going back.