Someone had marked the product as "Available Yes" but hadn't changed the release date. The date in the Release field was 8/27/2002 -- and the computer won't let you review a product if today's date is earlier than the release date, even if the product is marked Available Yes for some reason.
Whenever you want to indicate that a product is available you have to change both the Available and the Release fields (change "release" to one day before today in most cases).
I made the change and am seeing it on the list when I hit Add Review now.