|it might be a power saving feature, many laptops dim the LCD to conserve power when not in active use. If active use doesn't "wake" the display you might consider changing the system's power plan to "high performance." This can be done through the control panel. |
On a related note I have a Viewsonic monitor with adaptive contrast. When this mode is on, if the image on the majority of the screen is dark, the monitor adjusts the contrast, resulting in an even darker scenario. When I open up a brighter image (try google since it's mostly white) the screen becomes very bright. It's a technology with potential, but hasn't been perfected quite yet, at least not on my particular model.