Xvnc/Xnest/Xvfb can't create a socket in /tmp/.X11-unix.

The permissions to the /tmp/.X11-* directories have been restricted
for security reasons.

In order to still run unprivileged programs such as Xvnc/Xnest/Xvfb,
you need to start those programs with the "-pn" option.

You can no longer use displays of the form ":<num>"; only
displays with the full hostname will still work: "<hostname>:<num>".

The Solaris 9 versions of Xnest/Xvfb are able to create these sockets
as they also run set-gid.