getting vnc to work for me was a bit tricky. this will probably be different for you based on what window manager you run, but i use xfce4. here is my xstartup file for you to look at
Code:
#!/bin/sh
xrdb /home/administrator/.Xresources
xsetroot -solid grey
#xterm -geometry 80x24+10+10 -ls -title "$VNCDESKTOP Desktop" &
unset SESSION_MANAGER
startxfce4 &
i do not believe you need to use unset session_manager for kde and gnome. for your purposes, replace startxfce4 with whatever manager you are using... i.e. startkde
it might be possible to also use startx, im not entirely sure.