I have researched the solution...

gconftool-2 --type string --set /apps/gnome-power-manager/buttons/lid_ac "nothing"

does not fix it. I have two external monitors and when I close my lid the settings are reset and the laptop's monitor is set to the default.

Thanks!

gsettings list-recursively org.gnome.settings-daemon.plugins.power  
org.gnome.settings-daemon.plugins.power active true  
org.gnome.settings-daemon.plugins.power button-hibernate 'nothing'  
org.gnome.settings-daemon.plugins.power button-power 'nothing'  
org.gnome.settings-daemon.plugins.power button-sleep 'nothing'  
org.gnome.settings-daemon.plugins.power button-suspend 'nothing'  
org.gnome.settings-daemon.plugins.power critical-battery-action 'suspend'  
org.gnome.settings-daemon.plugins.power idle-brightness 30  
org.gnome.settings-daemon.plugins.power idle-dim-ac false  
org.gnome.settings-daemon.plugins.power idle-dim-battery true  
org.gnome.settings-daemon.plugins.power idle-dim-time 10  
org.gnome.settings-daemon.plugins.power lid-close-ac-action 'nothing'  
org.gnome.settings-daemon.plugins.power lid-close-battery-action 'nothing'  
org.gnome.settings-daemon.plugins.power notify-perhaps-recall true  
org.gnome.settings-daemon.plugins.power percentage-action 2  
org.gnome.settings-daemon.plugins.power percentage-critical 3  
org.gnome.settings-daemon.plugins.power percentage-low 10  
org.gnome.settings-daemon.plugins.power priority 1  
org.gnome.settings-daemon.plugins.power sleep-display-ac 600  
org.gnome.settings-daemon.plugins.power sleep-display-battery 600  
org.gnome.settings-daemon.plugins.power sleep-inactive-ac false  
org.gnome.settings-daemon.plugins.power sleep-inactive-ac-timeout 0  
org.gnome.settings-daemon.plugins.power sleep-inactive-ac-type 'suspend'   
org.gnome.settings-daemon.plugins.power sleep-inactive-battery true  
org.gnome.settings-daemon.plugins.power sleep-inactive-battery-timeout 0  
org.gnome.settings-daemon.plugins.power sleep-inactive-battery-type 'suspend'  
org.gnome.settings-daemon.plugins.power time-action 120  
org.gnome.settings-daemon.plugins.power time-critical 300  
org.gnome.settings-daemon.plugins.power time-low 1200  
org.gnome.settings-daemon.plugins.power use-time-for-policy true