Was it working before, or is it a fresh install that has never had X up and running...?
If you have an old copy of an xf86config-4 file around that you know works on your system, you can copy it across and then use it as a base to work from.
If it's a fresh install and has never worked, then you can always open up /etc/X11/XF86Config-4 with a text editor (vim or whatever) and edit the entries - particularly those referring to those modules that are causing it to crash. Alternatively, run <xf86config> to generate a new config file.
Hope this helps...
PS. A cheap and nasty (well, maybe not nasty) way around it all would be to boot from a Knoppix cd, and then copy the XF86Config file from there.