Howdy. I have an "early 2008" Macbook Pro 4.1 with 15" screen, running Lion. Until recently, operation was flawless. Now, when I turn on computer, I get a bit of flashing at first, with light horizontal lines across the screen, and lighter and darker sections. Then the screen goes black for about 30 seconds. Then everything clears up and the screen is fine. Clues? I'm thinking of taking the machine up to the nearby Apple store for a check-up. Appreciate any suggestions...is there a diagnostic I can run before I head for the store? Thanks!