Dithering

It's very possible that your brightness setting is a couple of clicks too high. The only way to know for sure is to run one of the calibration disc brightness patterns and veryify that you get absolutely no dithering on that pattern.

Another easy way if you don't have a disc is to pop in a blu-ray that is encoded in the 2.35 or 2.40 aspect ratio, then check if there is dithering in the black bars. If there is, then lower your brightness one notch at a time till it disappears. (feel free to get very close to the set to tell)

It is possible to then see dithering in the actual movie itself during dark scenes, but this is usually normal and attributed to the disc if it was a badly mastered disc.

On my Samsung e450 if I turn brightmess down till the dithering flickering pixels disappear I get too much black crush in the blacker blacks so I keep my brightness a lot higher than most.Unfortunately it washes out on bright screens though.if I go through grayscale ramps thoroughly I can reduce a tiny bit of it.
Edited by Vic12345 - 1/20/13 at 6:18pm

brightness is too high would be my guess. put up something that's supposed to be solid black, put your face right up to the screen, and turn the brightness down until you can see no pixels jumping.