Once my parents' Wirehaired Pointing Griffon kept barking incessantly at the fireplace/chimney for a period of weeks...it turned out there was a raccoon living in there. A big fat one. Yikes!
Abbylynn, might be worth checking out up there. But if not, taking the fixture out and putting it on the floor for Eddee to sniff around so he can get brave would not be a bad idea.