Late 2008 MacBook Air users have been reporting grey horizontal lines across the screens of their laptops according to Tidbits.
There have been slight variations in the description of the issue, but most accounts agree the lines are grey or white, horizontal or slightly angled, granulated or pixelated in appearance, and are very subtle. Overall the lines are said to give the screen the appearance of a piece of parchment or recycled paper. Also, the lines are said to appear at the initial boot; they do not develop over time. See what the lines look like for yourself in this photo.
Forum posters say that Apple has said there will be a fix in upcoming firmware updates. It is not known whether the delay in base model MacBook Air with HDD was because of this or a related flaw.