snowy type effect going on

[roi]

I just purchased a 50" LG plasma, and a Panasonic Blu-Ray player. I couldn't be happier with the television as far as it's picture quality when watching regular HD programming...looks great.
But, when I watch a Blu-Ray disc...I get this "snowy" type of effect going on. I purchased hi quality HDMI cable. Can't remember what type of cable, but the sales guy said it was the highest quality one.
Anyway, does anyone have any suggestions on what may be the problem?