I've been trying to get my card to work with fglrx for a while now but without any errors in the xorg log i would boot to a black screen and the machine would hang.
To resolve this issue i had to enter the bios (gigabyte) and press CTRL+F1 for advanced options. Within one of the menus is the option for AGP aparture size. Setting this to the highest setting (256) resolved my problem.
EDIT: This needs to be moved to the AMD/ATI Linux drivers section apologies for posting in the wrong section.