I have encountered this on both Windows and Linux (Ubuntu) machines having installed the latest ATI Catalyst drivers on a fresh OS install. In Windows, safe mode works normally, you can uninstall the driver and reboot to normal mode, where you can install the drivers again, or a different driver version of the driver. In Linux, you can Ctrl+Alt+F1 to the terminal and amend the X11.conf file to revert back to previous driver and re-install.
However all of this didn't make any difference to me, each time I still ended up with a black, unresponsive screen.
The solution: Have you got a TV plugged into an HDMI port? Turn the TV on and switch to HDMI input. What do you see? That's right, the driver defaulted the primary display to the TV and the monitor was showing the secondary display which has a black desktop colour. You can move the mouse over and open the display properties to set the monitor to the primary.
Several days wasted fixing this one.