Sony 46" Z series - ghost images

I connected my Sony 46" Z series to my computer using VGA cable. I have a decent video card (Nvidia 7300 LE). Everything works fine except there are ghost images. I know that they are not from the TV (the TV works fine when connected to cable). I changed a couple settings but couldn't get rid of those. Any suggestions?
Thanks...

(Could the problem be from the VGA connection? The video card has DVI out but the TV has only VGA in. Should I try DVI to HDMI connection?)

Thanks a lot for the replies. I'll certainly try the digital connection.