The problem in my case, and maybe yours, is that the Intel Core CPU (i3/i5/i7) have integrated graphics, and since I bought a notebook model that also have discrete ATI GPU, in a way that I have 2 GPUs at same computer, with the infamous 'switchable' option.
The bad thing is that Linux kernel is just starting to support switchable graphics, and worst, Xorg totally don't support it.
Be best (fast) solution would be to disable the switchable thing at BIOS, enabling only the ATI GPU. But to my bad luck, that's not an option to me, because there is no HP notebook with BIOS option about switchable graphics.
So fglrx detects something that it don't understand, and, so, I get the black screen thing.
I e-mailed HP asking them for a new BIOS version to disable Intel integrated GPU, so I would get only the ATI GPU detected by my favorite OS.
HP replied saying something that seems to be wrote by a bad-programed-robot, with all nonsense phrases, just copying and pasting my own words from the initial message.
So I replied their response asking for someone that understand what BIOS is. Some days later, a guy e-mailed me, he said that HP will not release a new version of BIOS, and if HP does, it will not contain the switch-off integrated graphics feature. dot.
The good thing is that I still can have hardware accelerated graphics from the i5's GPU. Intel have much better linux driver support than ATI. My KDE works beauty with all those transparency and animations.
Sad that I paid/waist $500 more on this notebook model just because of the ATI GPU and I can't use it.
I will have better luck on the next buying, keeping away from HP and ATI. Maybe a Dell with Ubuntu.