I have a 60pl9200d/37 phillips dlp 60" tv. The tv will work great clear and crisp picture for about 15-30 minutes then it fades to a greenish purple color and will not go away until i turn the tv off for about 5 minutes. I have unhooked all composite and hdmi cable and used only coax cables, thinking this may be the problem, but it will still do it. Any ideas on what the problem may be???