I have an Epson 5000 projector that on power up has green streaks aprox 2 pixels wide throughout the screen running vertically. after around 5 mins they disappear giving a perfect picture, no matter what the input. but... again after 15-20 mins later they re-appear, this time much worse and stay on screen. anyone have any idea what is wrong and how i can rectify this problem. please help! Thanks.