Nothing is coming out of my speakers, they are all plugged in right, then when i go to like volume on my computer it says there is no audio devieces. Then I restart my computer, and it works. sometimes my iTunes works, then I go  onto Youtubve, and that doesn't work. It goes on and off. But when I restart my computer it works. Then I turn the screen off for the night, I go back on in morning and then it doesnt work again. This has been happening forever!! I cant find any answers...