Hey mate, its just reverted to the standard setting. it dims the dash lights when the headlights are on so it doesnt blind u at night - people prefer it that way.
its adjustable though - turn on your car, turn the headlights on. Press the odo button and scroll through the option - (Odo, Trip A, Trip B)
When the headlights are on, you get a 4th option which is dashes. this indicates the amount of light for the dash lights (less dashes, dimmer light) to adjust, hold the odo button in like if you were reseting the trip, and it will scroll through the different light options.