gnome-power-manager and gnome-screensaver seem to be very confused by the closed lid. Looks like gnome-power-manager does not function once the lid is closed. gnome-screensaver at least starts the screensaver on the external monitor most of the time. I implemented a poor-mans version of screensaver management. I am running the following script every minute in crontab. manual-screensaver.sh :

Code:
#!/bin/bash

# this is a workaround for screensaver problems with external monotor 
# on lenovo. gnome-screensaver and gnome-power-manager seem to get 
# confused since the laptop screen is disabled and the lid is closed.

export DISPLAY=:0.0
SCREENSAVER=300000 #milliseconds
DISPLAYSTANDBY=600000

SS_STATE=`gnome-screensaver-command -q`

ss_is() {
    [[ "${SS_STATE}" =~ "The screensaver is $1" ]]
}

ss_is 'being inhibited' && exit

IDLE=`xprintidle` # in milliseconds

[ $IDLE -lt $SCREENSAVER ] && exit

if [ $IDLE -lt $DISPLAYSTANDBY ] ; then
   ss_is active || gnome-screensaver-command -a
elif ss_is active ; then
   gnome-screensaver-command -d
   xset dpms force standby
fi
In the screensaver configuration set the screensaver to start slightly later.