Comment 10 for bug 140590

Suspend seems to have two issues on the Latitude D820, Nvidia drivers and Compiz running.

The workaround is as follows:

1) sudo gedit /etc/X11/xorg.conf and make sure the following lines are there or match:

Section "Device"
        Identifier "nVidia Corporation G72M [GeForce Go 7400]"
        Driver "nvidia"
        Busid "PCI:1:0:0"
        Option "UseEDIDDpi" "False"
        Option "AddARGBVisuals" "True"
        Option "AddARGBGLXVisuals" "True"
        Option "NoLogo" "True"
        Option "NvAGP" "1"
EndSection

2) sudo gedit /etc/default/acpi-support and make sure the following are changed:

SAVE_VBE_STATE=false #ex-true
POST_VIDEO=false #ex-true
USE_DPMS=false #ex-true
LOCK_SCREEN=false #ex-true

3) gedit /etc/acpi/suspend.d/03-kill-compiz.sh

killall compiz.real

4) chmod 755 /etc/acpi/suspend.d/03-kill-compiz.sh

5) gedit /etc/acpit/resume.d/99-restore-compiz.sh

su - <your-user-name> -c "compiz --replace gconf"

6) chmod 755 /etc/acpi/resume.d/99-restore-compiz.sh

And that should do it. Of course, your could just disable desktop affects, but that wouldn't be any fun.