I believe that it takes some time for the proteins to come out of solution as the beer chills (colder = faster) then they have to start sticking together for you to be able to "see" them.
My chill haze "solution": 31 deg F for a week, 1/2 packet of gelatin dissolved in 1/2 cup of the target beer, add to beer while still over 100 deg (so the gelatin solution will stay at the top). 2 days later you have clear beer!