I don't believe you can just change the XF86Config back to using the stock drivers without also uninstalling the nVidia GLX drivers (originals are restored during the uninstall). Things may have changed but that's the way it used to be.
Did you happen to play with firewall settings around the time the problem began? It should be using local unix sockets so that shouldn't really cause a problem thought... Just thinking out loud... Also, what is the output of:
# netstat -a | grep 7100
In addition to the X socket having improper permissions, so could the xfs socket directory which is "/tmp/.font-unix". What do these commands show:
# ls -al /tmp/.font-unix
# ls -al /tmp/.X11-unix


