We are having the same problem with our 19 month old son. And not for a week, but since mid-March. Black-out curtains, water and snack in the crib, snack right before bedtime, early bedtime, later bedtime, playing hard before bed, etc. He naps once a day, he is in daycare so very stimulated all day, he is in bed between 6 and 7pm each night, we NEVER get him before 6 (this obviously isn't working to teach him an appropriate wake up time), we can't figure it out! I'm watching this thread so I can learn something too. Bedtime makes absolutely NO difference. He needs 11 hours of sleep and he's not getting it. But you're not alone in this misery. And I've seen some threads where people complain because their kids get up early - at 7:30 or 8 a.m. All I'm asking for is 6am. 6!!! :)
Did I mention we have a 5 month old who gets up twice to eat during the night? I shouldn't complain. I love my children with all my heart. But I'm so tired.