I have Oracle 6.3 and found that Xvfb refused to recognize the fontpath.d directory
"Could not init font path element catalogue:/etc/X11/fontpath.d"
I verified X was working by sending xclock to my display, so it was Xvfb centric problem.
I took advice and did the following: from - http://singcheong.blogspot.com/2013/...ith-fixes.html
sudo yum -y install libXfont
This got rid of the error and Xvfb is now running!!!