My laptop has WinXP Pro SP2. After working correctly for about a week, icons and some more graphical features, like button frames, disappear. If the icon is for a link, then the small arrow that signifies it remains. Clicking on the empty place of the icon works as if the icon was visible. For an interesting feature, when I try to log out, the computer might show the window saying that some application's state is being saved, but the application's name in the header is invisible. Logging out and in again solves the problem for that user, but not for others. Rebooting altogether gets rid of the phenomenon.