Panasonic TH-50PHD7UY Plasma TV Monitor and on my direct tv cable and comcast HD cable there is a faint clear to white line and at times alomost undectable that raises vertically. I do not see it on dvd's. I run my compent video cables into my NAD receiver and than one component out to the tv. What could be the cause of this line and more so how do I get fix it?