Screen auto-dimming when I hit delete

I bought a 17" macbook pro for school three weeks ago. It is 2.5ghz, 4gigs of ram, 250gb hd and the high res scree. I upgraded from a 17" powerbook g4.

One thing I have noticed that really bugs me is that when I hit the delete key the display will dim as if I where to turn out the lights and it will light back up when I take my hand away. I only hit the delete key for just a second and it does this. It is quite annoying that I never had a issue with on the powerbook. I assume the light sensor is right around there but it would seem that apple would make it so it would take longer then a second of darkness to dim the screen.

I am sure someone else has had this issue as well.

Thanks,
-rob