Every so often I notice that on my unibody MBP there seems to be only what I can describe as a power line that flashes in the middle of the screen for a second and then disappears. It does not happen every time I use my computer. I am not sure what is causing it since I can't replicate it and it seems to occur randomly. The other day I was watching a YouTube video and all of the sudden the screen went black and had a line or two of scrambled pixels at the top. I restarted and everything was fine. Since then I haven't noticed either problem, but I am concerned that there could be a problem with the graphics card or some other piece of hardware. Should I be concerned about this? Should I take the comp to an apple store or just monitor the problem for now?