I suspend my laptop by closing the lid, but when I open it my screen stays black, when I should be prompted to enter my xscreensaver password.
The screen is "on" because I can switch TTY using Ctrl+Alt+{1,2,3,...}
(and login if I want), but the xfce session running on the original TTY is just black with no mouse cursor visible.
Before the screen goes black, I briefly see a command line login prompt, which suggests that my session has been logged out of the command line behind xfce. This could be a feature of the server edition of Ubuntu that I am using.
If I switch TTY and kill my xfce4-session
process, it causes the original TTY to go back to the gdm login prompt, and I can login again without the need to reboot my laptop. I am using this as a workaround for now. Also, it is not a problem with xscreensaver, because I have tried uninstalling it, and the problem remained.
This is a Dell Inspiron laptop with an integrated Intel graphics card.
During the upgrade process to 15.04, I was asked if I wanted to replace my grub configuration file, because the package maintainers version was different. I elected to keep my existing configuration. Could this have anything to do with it?
Warning: Some of the instructions posted as answers can potentially break your installation.