or being a tad more savy on your resources and not use the virtual framebuffer by changing your xstartup script in the .vnc (hidden) folder. one I use looks like (with xfce)
$this->bbcode_second_pass_code('', '
#!/bin/sh
xrdb $HOME/.Xresources
xsetroot -solid grey
xterm -geometry 80x24+10+10 -ls -title "$VNCDESKTOP Desktop" &
#twm &
startxfce4 &
')
you can substitute lxde, xfce, blackbox, fluxbox, openbox etc at your convenience. then start your session with
$this->bbcode_second_pass_code('', '
vncserver :1
')
kill it using the -kill command switch