I have a macbookpro unibody late 2008 15p and use OS X Lion, 10.7.3. I use always an external monitor and close the lid. When I finish my work day I put the macbook in sleep mode and it switches off. The next day I want to switch on my mac so the previous state appears on screen (in my external monitor). But 20% of the times it happens that external monitor screen is black, and if I open the lid, macbook screen is also black, but the laptop is switched on. It seems that for some reason the screen output does not work. Since I do not want to lose all my open windows and documents I try to put it again in sleep mode and reboot, but the combination cmd+alt+eject and others do not work here and the macbook remains switched on.
I already tried resetting PRAM and other similar things.
So at this point I would like to know whether this can be solved.