If you have a misbehaving keyboard mapping when you connect to a tightvnc VNC server running under Ubuntu from a Macintosh OS X using any of the VNC clients add the following to your VNC server's xstartup script
# See https://bugs.launchpad.net/ubuntu/+source/vino/+bug/112955
export XKL_XMODMAP_DISABLE=1
Thanks Geoffrey for the help.