It's an xorg issue, have you tried:
$ sudo aticonfig --adapter=all --initial -f
If you haven't run the above 'aticonfig' command yet it's required to populate xorg.conf file before running miners and GPU.
If using a USB flash drive, then:
$ sudo sync
(not required if installed to a hard drive.)
Reboot the system:
$ sudo reboot
$ sudo shutdown -r now
Did you follow an install guide? Which one?
Could you run:
$ apt-cache showpkg fglrx
It should return information about which version of fglrx is installed, example:
The * would be the version of fglrx installed.