I tried to use tightvnc back in August and had some help, but I stopped 
due to IPv6 support.  Now I am back at tightvnc and cannot get the 
server started.  This is on a new Centos install that did have regular 
vncserver working on it (I did a yum erase vnc-server first).
So I have a working /etc/sysconfig/vncserver and my user has the 
appropriate ~/.vnc files that worked with regular vnc.
Logged in as root, I issue:  service vncserver start
and get:
Starting TightVNC remote administration daemon (Xvnc):2:root WARNING: 
initlog is deprecated and will be removed in a future
vncserver: The USER environment variable is not set.
                                                           [FAILED]
But there is a USER environment variable set:
set|grep USER
PROMPT_COMMAND='echo -ne 
"\033]0;${USER}@${HOSTNAME%%.*}:${PWD/#$HOME/~}"; echo -ne "\007"'
USER=root
(remember, I am logged in as root so I can issue the service command)
And further in /etc/profile I have:
if [ -x /usr/bin/id ]; then
        USER="`id -un`"
        LOGNAME=$USER
        MAIL="/var/spool/mail/$USER"
fi
The only line in the /etc/sysconfig/vncservers is:
VNCSERVERS="2:user"
where user is the userid.