I've modified my /etc/X11R6/bin/startx file and added this

for display in 0 1 2 3 4 5 # checks for open display, starts X on next available
{
if [ ! -f "/tmp/.X$display-lock" ]
then
exec startx -- :$display
fi

to startx in a different display number. This is able to get the next available display number but, after two X terminals already open, I get the following error:

..
AUDIT: Mon Nov 26 12:58:22 2007: 13052 X: client 1 rejected from local host
Xlib: connection to ":2.0" refused by server


I don't understand why it is being refused.