You could run an Apple Hardware Test which might give you a clue as to the problem. I suspect though that your best probability for a resolution lies with the Apple store genius bar.
You can also check your Energy Saver "Display Sleep" options.
Is it possible you have set a Hot Corner to put the Display to sleep?
I use this feature so that when I know I'm walking away from the comuter but need to it to stay on, I slide the mouse cursor into one of the 4 corners of the screen and it puts the display to sleep.
These are configured in System Preferences > Desktop & Screen Saver > Screen Saver > Hot Corners
MacBook Pro 13" 2.53 GHz unibody
After servicing the trackpad on this unit I noticed a random black screen that persisted shortly after startup. It was not a normal sleep - no way to wake the machine.
SMC reset by the recommended Apple procedure did not help the problem. To repair perform the following:
1) unplug MagSafe power supply
2) remove bottom case
3) carefully disconnect battery
4) plug in MagSafe power supply
5) open the laptop and rest it on the LCD case
6) perform Apple recommended procedure for SMC reset
At this point you will (hopefully) notice that problem has vanished. In energy preferences you can slide all the controls for battery and power supply to never. Test it for a while on the MagSafe
8) plug in the battery (no need to power down)
Test the for the black screen issue running on the battery. For me at this point the problem had totally disappeared! Once your satisfied that its working:
9) power down
10) unplug the MagSafe
11) replace the bottom case