We're in a rut

I have always had two GREAT sleepers. I am serious!!! They both sleep 11-12 hours a night. They have always taken great naps. In fact, Ethan still enjoys a good nap now and then. For some odd reason, we have had the hardest time getting Link down for bed this past week. He comes out of his room 42 times before we break down and put the baby door knob on. Then, he cries for another 30-40 minutes. I eventually get sick and tired of the screaming and go up there with my "angry" voice! Only then will he finally go to sleep. As I type this the entire DC metro area is listening to him screaming "MOOOOOOOOOOMMMMMYYYYYYYYYYY!" We have to break this cycle and quickly....before I lose my sanity!