RE: Latitude E7440 black screen after undock
Elwardo, I've been researching this problem as I have a couple of E7440s that are doing it randomly. We've found that people having problems are wearing wristwatches that use a magnetic clasp, and the magnet triggers the "Lid closed" switch inside the laptop. That makes the machine go black, although it's not consistently going to sleep, because the magnet is often moved away quickly so it 'wakes back up' but the screen stays black.
Just curious if you wear a watch with a magnetic clasp. I figured this out when I had E7440s stacked on top of each other in my office and moving them would put them to sleep (or wake them up). I though I was bending something. Started researching more and found magnets are in the lid and a magnetic switch is in the case to tell the bios if the lid is open or closed.