It might not fit all the facts as reported, but could it be that you have Easy Exposure Compensation enabled? Then the compensation value would change every time you turn one of the Command Dials.See Custom Setting b3 on page 212 of the manual for details.
BrianWelsh NikonianCheck out the Nikonians Team pages
Copyright © Nikonians 2000, 2013
All Rights Reserved
Nikonians®, NikoScope® and NikoniansAcademy™ are trademarks owned by Nikonians.org.
Nikon®, Nikonos® and Nikkor® are registered trademarks of Nikon Corporation.