colors from graphic card gets sometime inverted

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http://askubuntu.com – Colors from graphic card gets sometime inverted. When I start Ubuntu 12.04 its just fine, but sometimes after some time the colors get inverted. I use a 40" lcd-tv as a monitor, and if I cahnge the cannel and then turn it back its ok again for some time and then it happend again. I have a "Sapphire Radeon HD5450 DDR3 HDMI 1GB" and a 50HZ SONY TV. I have a dual boot so it happens the same in my Windows 8, I have a nother computer connected to my TV and I have never had a problem like that earlier. (HowTos)