Xvfb dead but pid file exists

#!/bin/bash
#
# /etc/rc.d/init.d/xvfbd
#
# chkconfig: 345 95 28
# description: Starts/Stops X Virtual Framebuffer server
# processname: Xvfb
#

. /etc/init.d/functions

[ "${NETWORKING}" = "no" ] && exit 0

PROG="Xvfb[
PROG_OPTIONS=](7)
-ac -screen 0 1024x768x24"
PROG_OUTPUT="/tmp/Xvfb.out"

case "$1" in
    start)
        echo -n "Starting : X Virtual Frame Buffer "
        $PROG $PROG_OPTIONS>>$PROG_OUTPUT 2>&1 &
        disown -ar
        /bin/usleep 500000
        status Xvfb & >/dev/null && echo_success || echo_failure
        RETVAL=$?
        if [ $RETVAL -eq 0 ]; then
            /bin/touch /var/lock/subsys/Xvfb
            /sbin/pidof -o  %PPID -x Xvfb > /var/run/Xvfb.pid
        fi
        echo
   		;;
    stop)
        echo -n "Shutting down : X Virtual Frame Buffer"
        killproc $PROG
        RETVAL=$?
        [ $RETVAL -eq 0 ] && /bin/rm -f /var/lock/subsys/Xvfb /var/run/Xvfb.pid
        echo
        ;;
    restart|reload)
    	$0 stop
    	$0 start
        RETVAL=$?
      	;;
    status)
    	status Xvfb
    	RETVAL=$?
    	;;
    *)
     echo $"Usage: $0 (start|stop|restart|reload|status)"
     exit 1
esac

exit $RETVAL

ps aux | grep Xvfb