Hi all, this issue began spontaneously, I don't know what triggered it, I take good care of the computer. I've tried to start up while holding command - R, resetting the PRAM, etc to no avail. I'm an engineering student and I'm on this thing all day so I'm beginning to get anxious. Command R takes me to Internet recovery, but I get an error message every time saying Apple.com/support, 6003F. I've looked this up and nothing has helped, I would appreciate some help on this one!