Mobility Radeon HD 4850 no screen found with fglrx

Question

hi there!
I've recently been trying to install arch on my iMac 11,1.
The first problem I encountered: black screen as soon as I booted the live CD. After a quick search, i leaned that this could be fixed easily by adding "nomodeset" as a kernel parameter. But that leads to another problem, this time with the radeon driver. According to the KMS section of the radeon driver, using KMS is mandatory to the radeon driver, wich leaves only the catalyst ones for my setup.
Since I don't really mind about the drivers I use (as long as it actually works), I went and installed catalysts following the instructions here.
Problem is: X crashes on boot. A black screen is displayed and nothing happens.
fglrxinfo returns
Error: unable to open display (null)
my xorg.conf (generated with "aticonfig --initial")
http://pastebin.com/etdPdtuD
and the last log from Xorg start:
http://pastebin.com/Rzx4fqx7
here is the relevent section of lspci -vv
http://pastebin.com/emgAWzXr

Answer 1

O and just saw this little section from the first link...down by configuration
Option "MacModel" "string"
    Used to specify Mac models for connector tables and quirks. If you have a powerbook or mini with DVI that does not work properly, try the alternate options as Apple does not seem to provide a good way of knowing whether they use internal or external TMDS for DVI. Only valid on PowerPC. On Linux, the driver will attempt to detect the MacModel automatically.
    ibook -- ibooks
    powerbook-external -- Powerbooks with external DVI
    powerbook-internal -- Powerbooks with integrated DVI
    powerbook-vga -- Powerbooks with VGA rather than DVI
    mini-external -- Mac Mini with external DVI
    mini-internal -- Mac Mini with integrated DVI
    imac-g5-isight -- iMac G5 iSight
    emac -- eMac G4
    The default value is undefined.