Are you running something like AUI? I have noticed that for some reason, it won't show me actual Experience, but Champ Experience no matter how I fiddle with the settings. If you come off of Enlightenment, then your exp shown in the UI will be about what your seeing vs what is shown while enlightened.
It does sound like you're just experiencing the drop out of enlightenment.
Did you outlevel your area? And as Nestor hinted at....were you enlightened?