Ubuntu 12.04 doesn't start or install

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http://askubuntu.com – I have an HP G4-1387 which has two graphics cards, an ATI 7450M and Intel HD3000. I tried to install Ubuntu and run it from my USB stick, I get the usual black, console like screen showing a lot of things in an small resolution, then the screen adjust the resolution and then it is suppose to start Ubuntu or installation but instead I get a black screen forever. I think is related to a graphics card driver problem. Any idea how to solve it? Thank you (HowTos)