Display Issue With Vista/Media Center

I have my tv connected to my computer the SVhs cable and set up as my primary
display so I can use Media Center. I went through all of the steps to set up
Media center, watching them on the tv screen. When it came time to get to
watch tv, through Media Center, on my tv, the screen was white. I had sound
but no picture. After moving the mouse around, the rest of the screen came
up but the feed was white. Can anyone help me figure out what's going on or
how I might get this problem solved?