I recently bought the dell Inspiron 3542 (Ubuntu-certified), it came preloaded with Ubuntu 12.04, I did a clean install of Ubuntu 14.04 (erased everything).
When I try sudo pm-hibernate
the computer shuts down and when I start it, my apps won't reopen.
I have 4GB of ram and a 4GB swap partition that is never used(shows 0.0% in system monitor), I think that's because I never overloaded the laptop.
Note: when i login after a failed hibernation, i get this window :