Inability to fall asleep at night after taking evening naps. You come home from work and take a nap from 7-9. As a result, you can't fall asleep until well after midnight. The next day, the same cycle repeats itself and so on and so forth.
"You've crashed on the couch after dinner the last two nights and then haven't been able to fall asleep until 2 a.m.? You must have Evening Nap Syndrome (ENS)!"