ATI drivers tend to fail on startup when xorg-server is built with the ipv6 useflag. There should be a note informing users about trying to rebuild xorg-server without that flag. It caused me a lot of headache and it turned out to be known at ati upstream. So please add some ewarn :)
I cannot reproduce it at all, which are the exact conditions triggering it? Does it happen with the latest drivers?
happens with latest ati drivers and current xorg-server (arch and ~arch) and disabling ipv6 support in the server makes it work. I'm not fully sure what really breaks there but a toggle of that flag makes it go insane or work.
seems to be fixed in latest version