Problem after upgrading VGA

[metallo97]

Hi all, got a ML install working 2 months ago with this config: Q6600, Biostar TPower I45, 6GB DDR2, 140gb SATA HDD, Sapphire 5850. Then i sold the 5850 and bought a 7950. Now, it doesen't boot and it displays the stop sign.

This is what it tells me on verbose:

 

Thanks everyone who will answer