I first loaded my game with Minecraft 14w21b. Then when I loaded the game in 1.7.9 the screen flickers white when I play but not on the title screen. It does it on servers too.
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qmagnet
MC-58999
My Screen Keeps Flickering When I Play
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qmagnet
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Minecraft 1.7.9
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I've had that issue in the past. It was caused by skype specifically but I think it was due to too many programs running. I'd check to see if you have any ghost Java processes running in the background.