It could be a board or a color wheel issue. I'm not able to offer a definitive diagnosis, but I'd recommend having the unit inspected.
My Samsung DLP TV HLR5667w has been giving me checkered patterns on the screen lately. It will go away for awhile if I uplug and replug the TV. I know that it is not the cable because my other TV's do not have the problem and the problem still occurs on the antenna mode.
The channels will also freeze for a bit and then continue. Sometimes the picture will freeze and the sound will continue as normal. The TV will shut off by itself and sometimes will not start for several minutes.
Below are some examples of the picture. Help please, the TV is about 3.5 years old.