have you tried running 'fglrxconfig' yet?
If so and still problems type 'mcedit /etc/X11/XF86Config-4' or use any text editor, vi, etc, scroll down to around line 315 where the monitor and next sections are. check them out, especially the resolutions wheich are under the 'screens' section in like 476 or so.
no screens found means that the config file cant find a useable resolution to display anything.
post ur screen section here this doesn't work.