MBP display dimming

Hi, I just got a new MacBook Pro, and for whatever reason, the screen is dimming after a few minutes of being idle. It's hooked up to an external monitor that isn't dimming. In the displays preference pane, I unchecked the "automatically adjust brightness" box, so that's not it. In the energy saver prefs, I told it to never ever dim the screen, and I did that for both the power adapter and battery profiles. The screen is still dimming after about 15 minutes, though, and it's immensely irritating. Does anyone have any ideas? Everything google turns up is that it's one of those two prefs, but I've checked them both and it's still an issue. Thanks.

How about the screensaver?

Also try caffeine
Lighthead - Caffeine

Try resetting the System Management Controller (SMC). That controls the ambient light sensor among other things. If that doesn't work to stop the screen from dimming, make an appointment with Apple and bring it in to them to look at. That should not be happening with a new machine.

Regards.

In addition to what's been said, did you turn off the automatically reduce brightness before going to sleep? Try increasing your sleep time if that doesn't work. Since it only happens when you keep your computer idle then I believe it's related to the sleep mode dimming feature. If nothing works then bring in to Apple like chscag said.