My Toshiba's screen keeps going to sleep whenever I 2 finger scroll on the touch pad and I can't figure out how to stop it. I have tried looking through all the keyboard, touch pad, scrolling and screen settings and nothing seems to show why this would be happening. I have just had my screen replaced after the inner screen (LED/LCD) was damaged.
If the cable that connects the display is positioned incorrectly inside, or has a loose connection, that could easily cause your problem. Assuming you had it replaced by someone/someplace, I would have them relook at it and resolve the problem.