Fedora Hardware :: Unable To Use 12 With An Onchip Intel Video Card

I recently installed Fedora 12 and have tried it in different machines with different results. I am using HP laptops and can boot with no issues in one of them (HP NX7200), boot with compiz limitations in another (Compaq 6910p) and almost never get a proper boot on another (HP EliteBook 6930p). This last one is the one I want to check on, because even if I have got it to boot properly, most of the time it fails. I get to the login screen OK, but when trying to load the desktop, it usually fails and sends me back to the login screen. The driver in use is i915. I have tried to generate an Xorg.conf file and add a specific option, which I got from other people having the same issue. Here's the display section from my xorg.conf file:

Section "Device"
Identifier "Videocard0"
Driver "intel"
Option "Legacy3D" "true"

Looking into the last few lines from my Xorg.0.log file, I could see segmentation faults and messages that showed how the server was killed and the system would drop it. ometimes I can get this machine to boot (in fact, I am typing these lines from it). To achieve that, I run

su -c system-config-display

on one of the other laptops that work. That allows me to boot fine at least initially. Every time I get that right, I get a kernel crash message, which reports the following:

------------[ cut here ]------------
WARNING: at drivers/pci/dmar.c:616 check_zero_address+0x7d/0x191()
Hardware name: HP EliteBook 6930p
Your BIOS is broken; DMAR reported at address zero!

[code]....

If I reboot/shutdown, I won't be able to boot again until I repeat the same workaround.