I'm pretty sure that Jared has it right that it is outgassing from the coatings applied to the board or from the cleaning process. That is what the "New Car Smell" is - outgassing from the plastics and coatings on the interior. This is also, BTW, what caused a "smoker's film" to build up on the inside of the windshield and windows without the need to smoke ;-) Armor All and related products can also cause this as they outgas over time.
Hal
Harold Foster