The past two years there have been blackouts for the week before and after Easter. You can check Mary's site for the history of the exact days. In the past you could book during a sale/code and get it throughout your stay, but with the new 2008 system, even if you got a discount for one night, each night is separate, so the higher rates would go into effect. I haven't looked, but am guessing the rates are pretty high considering that this is peak holiday. This new 2008 rate system will have a huge impact on the cost of rooms now. Good luck!
Here's last year's from the history (note that Easter was 4/8/07 and the discounts stop at 3/30 and don't start again until 4/15 -- a week after Easter Sunday)
2/15/07-3/30/07 Annual Passholder room-only rates 1/3/07, exp 3/30/07
2/15/07-3/30/07 Florida resident room-only rates 1/4/07, exp 3/30/07
4/15/07- 5/23/07 package and room-only discounts for general public 3/8/07, exp 4/14/07
4/15/07-5/24/07 Annual Passholder room-only rates (until approx. 3/6/07, the check-in dates were 4/15/07-6/2/07) 2/21/07, exp 5/24/07
Here's the history from 2006: Easter was 4/16/06 (again the discounts stopped prior to Easter and then didn't start up again until a week after Easter Sunday).
2/16/06-4/13/06 Annual Passholder room-only rates 1/10/06, exp 4/8/06
2/20/06-4/8/06 Florida resident room-only rates 1/5/06, exp 2/8/06
4/23/06-6/3/06 package discount for Disney Rewards Visa cardholders 2/20/06, exp 3/30/06
4/23/06-6/3/06 Annual Passholder room-only rates 2/22/06, exp 6/3/06
4/23/06-6/3/06 Florida resident room-only rates