Mackenzie was a champion sleeper until she hit about 14 months. Being put into her cot was the worst thing in her world we could do to her and like you it was only a problem for her night sleeps, during the day she was fine. She eventually grew out of it (I agree with the others - she became more aware of what was going on etc) but her sleeping was broken through out the night and she would wake up screaming for sometimes hours at 2am. Once we moved her into a bed she was great - don't know if she felt confinde in the cot or she was just that bit older and she grew out of waking up etc.