[CentOS] centos 5.6 and intel MHD4500 graphics card

Hi!

I've a toshiba satellite notebook, and I tried to install centos 5.6.
The installer starts, but when it turns to graphical mode, the backlight 
goes off. I see the windows, buttons, but it's very dark, maybe the 
backlight switching off..

How can I get the installer to work correctly?

The machine details:
core i3 330m (The graphics controller maybe integrated to the cpu...)
it's a MHD4500 (GMA4500)

Thanks: Balazs