Hi, Jean! The Walt Disney World special offers for members of the military webpage can be accessed
here. After reviewing it, I see that there are blackout dates applicable to this year's special offers.
The resort discount states, "This offer is valid for stays most nights now through October 1, 2011. Discount is not valid April 17 – April 30, 2011."
The ticket promotion states, "In addition, Disney 4-Day Military Promotional Tickets (including any options) for the Walt Disney World Resort may not be used on the following blackout dates: April 17, 2011 through April 23, 2011, at all Walt Disney World Theme Parks and other gated attractions; and July 4, 2011 at Magic Kingdom Park."
I am not sure if blackout dates have ever been in effect before, but it is clear that they are in place for this year. I hope this answers your question.