I have a Mitsubishi WD 57731 DLP TV that I have had for 17 months. It has been working fine but a month ago developed a problem where the picture will dim very slightly for less than a split second like a quick flicker in brightness This happens intermittently. Sometimes it has to be on for awhile before it starts and sometimes it happens right away. It will do this about every 10 minutes or so. Has anyone had this problem or know what it might be? Thanks