I have a Dell Inspiron 15R with Intel® Ivybridge Mobile Graphics. I upgraded to Ubuntu vanilla and the latest version (16.04) few days back. Each time I close the laptop lid with the power source plugged in, and reopen it, a blank screen appears. A forced restart using the hardware button is necessary at this point. If the lock screen is activated, after a time it goes black. Even when on plugged on or on battery, if unused or locked, the same happens and a manual reboot is required for it to start. The CPU is running but I cant get to the login screen
Seems to match something I've seen already for 14.04:
File a new bug, and for now try the workaround from here:
map some key combination to:
xrandr --autoand you'll get your screen back by pressing it.