xserver ati/intel black screen "End desctription of problem"

Laptop:HP G-72
Graphic:Intel i915(core i3) and Radeon HD 5470

After Ubuntu 12.04 is installed I reboot and I got black screen.I started filesafe mode and updated the system to 12.04.1.I got balck screen,too.I generated with "> X -configure" the xorg.config file and edited it (I removed obsolete monitors and screens).
And got black screen.After it I edited xorg.conf and added to "radeon" option that set hardware resolution of my notebook screen´s (for my notebook:1600x900" ) and added "Modes" to "Monitor" (1600x900,1024x768,800x600) . After reboot i got black screen but background light was on and I heard the sound played fo login scrreen and I got Terminals tty1 to tty6 but it don´t work always but often.A change to vt-7 is after it impossible.When I am in terminal and nothin do , screensaver start to work and screen is black and keyboard don´t work.It all seems that automatic hardware config of driver or server don´t work properly.The second problem could be that allocation of memory don´t work (i am not programmer). And on the end the booting with splash screen that can i see works but after it black screen. This problem have all laptops with HD 5470I hope that this writing help developers to find the error.