I've been having this problem for a while now and I've been keeping my eye on Google but no solution has come up. A few people have posted the same problem, but there are no followups in those threads. So I thought I'd post here. I have an external monitor connected to the macbook and I have displays icon on my menu bar. If I can, I usually use both the macbook monitor and my external monitor. I think this is normal for many people. Now the weird bit. My macbook, completely randomly goes to sleep. Everything would go dark and the sleep light would start blinking. To wake it up again, I'd hit a key and it'd wake up. And then fall asleep again. The number of times I have to do this is also random. And then suddenly, my macbook monitor would stay dark, the sleep light would be solid white (not blinking like when it's sleeping) and the only monitor that'd work is my external. And it's not an extension of my macbook monitor like it is when both are on, it's my only monitor. So my dock and icons and menu bar are all in my secondary monitor. If I click on the displays icon in the menu bar, it only shows the external monitor in the list. And clicking detect displays has no affect. It's as if my macbook has lost track of it's own monitor. The only way to get it back is wait for the sleep light to turn off. This could take hours or days and then click on detect displays. Then my macbook monitor starts functioning like my primary monitor and my external secondary. I should mention that the random sleeping only happens if my macbook monitor is working. It never happens if my macbook is forcing me to use the secondary monitor. Sorry it's a bit of a read. not sure if I explained my problem clearly enough. I would like to know what kind of information I'd need to provide if order for someone smart to have a look into it. I have no idea where the problem could be. But that's because I have no idea how these things work. Thanks a ton!