I get that, too, but not very often.  I wonder if it has something to do with the automatic brightness adjustment that happens with changes of lighting in the environment?  I guess there's only one way to find out and that would be for me to turn the setting off and see if it stops.

It doesn't really annoy me too much, though, and I can live with it as long as there is nothing about it that signifies something will soon malfunction.

Thanks for your responses.  I went ahead and ordered one of those cases someone on here mentioned earlier.  I guess now I'm going to make the final move and order the 16GB model.  I want to pre-order it so I can get that $25 gift certificate, and if what I've read online is correct they might start shipping on July 12th or so, so I want to order before then.