This "dimming" issue occurs for some users when the action that they are calling for (i.e. open email, play movies, music, etc.) has more than one app that can complete the function (multiple email apps, movie players, music players, etc.). What is happening is a popup window is coming up but unfortunately, the window is not being drawn properly and is not completely visible. By rotating the screen, you are forcing the popup window to redraw correctly (allowing the screen to "calibrate"). This will only need to be done once. Once the screen is "calibrated", all is good.