Did you have blocks on the screen?
Basically everybody at some point is going to experience macro blocking and it's because the provider is compressing to much to fit all the HD content into the provided bandwidth. Hence why you see blocks form every once in awhile on the screen.
MPEG 2 encoding is a lossy compression based on Discrete Cosine Transformation (DCT). It breaks the image into small rectangular areas called macroblocks. Within these blocks the grid of picture elements (pixels) are encoded to represent their horizontal and vertical video frequencies. It does this so that when it has to throw out some information, it starts with the higher frequencies (finer detail) and works its way down.
Motion vectors is another compression technique that MPEG 2 uses to take advantage of redundant frame-to-frame information. The use of motion vectors allows the amount of DCT compression to be decreased. If there is so much motion that the encoder cannot keep up, it can no longer effectively use the motion vectors, and the amount of compression is increased. Fine detail is eliminated in each of the blocks, and what's left is more of an average. Since each block probably has a different average, it makes a mosaic looking set of squares on the screen. When things slow down, and the encoder can decrease the amount of compression the detail will return.
Did you watch both football games?
Did it happen in both football games?
CBS - Broadcasts in 1080i
FOX - Broadcasts in 720p
Are you having what's called Motion Blur?
You should be able to display HD sourced material and get a clean picture. The SD content on the other hand will look like it's a little grainy but tolerable and it's something that your going to have to live with. This is not the TV's fault but the source. This is one of the adjustments that people are going to have to get use to when they make a switch from a CRT TV. The bigger the screen the more evdent it will be.