It happened few hours ago - I tried to switch the MacBook Pro mid 2012 on from sleep. It doesnt switch on for some reason. I then shut the lid and suddenly the apple icon behind the screen lights up and I open the lid. But what I see is a screen of vertical stripes only in various colors, mainly different shades of gray. How do I fix this and why did this happen?
This is a common problem with 2012-2013 Macbook pro's, and is caused by the connection to the GPU card cracking. Apple is offering a repair program where they will fix this for free. If you have an Apple Store near you, I would suggest taking it in and having them fix it.