Hi all, Got a brand new 21.5 inch iMac last week. The screen randomly turns black without any major reasons. It doesn't seem to be a sleep mode/screen saver thing as the music continues to play on. I can adjust the volume or pause the music with the keyboard but the screen just won't turn back on. I have to shut it down using the power button and it happened several time the last couple days. Anyone else experience the same thing and got a solution? Thanks!