well there's something in your new XF86Config-4 that's not right then. if i were you i would run xf86config again and play around with the settings. try using default values and so forth instead of giving your exact make and model numbers. I have an ATI rage graphics card and it needs to be a generic card in the XF86Config, if i use the correct video card setting it has display problems.
remember to keep your old XF86Config-4 files and not overwrite them. The one you had before will now be at /etc/X11/XF86Config-4.old so if you do that 'mv' thing again, you will overwrite it. every time you change your XF86Config-4 file, rename the old one to something different, like XF86Config-4.crapcolours or XF86Config-4.blackscreen or whatever. This way you haven't deleted your old one if you want to roll back to it.
I don't know much about the XF86Config file to be honest, i sorted mine out by trial and error, which is as good a method as any in my opinion, as it lets you get your hands alittle dirty as it were. no doubt somebody else will come on here to help though...
good luck!