radeonfb is not working properly with IGP 340M video card

My laptop comes with an ATI IGP 340M card. Radeonfb has never been working properly since I put linux on my laptop.
I have tried every version of 2.6 kernel but no luck so far. The symptom is hard to describe, so I shot a short video of my screen (still picture doesn't do the job)
to demostrate the effect.
Here's the link to the video, hosted on my ISP webspace:
http://members.cox.net/bug.avi (3MB Xvid4 encoded)
Xorg works normally. Just the display in console is messed up.

My system: LFS 5.1
Kernel version: 2.6.5 (i have tried 2.6.6 and 2.6.7 up to rc3)