This has been very frustrating as I initially thought Ubuntu would not sleep because of the graphics drivers. I figured out it would not sleep when the mythtv backend service was running. It would just sit there with a blinking cursor and totally unresponsive.
To have Ubuntu disable mythtv backend service before sleep and start it again after waking up we need to add a file to /etc/pm/sleep.d/*file name*
#!/bin/sh case "$1" in suspend|hibernate) stop mythtv-backend sleep 3 ;; resume|thaw) start mythtv-backend ;; esac