Special price reverts at checkout

We just went live with our cart, and customer 1 noticed something we missed (drat). Zen Cart and db patch level both version 1.3.9h, MySQL 5.1.55, PHP Version: 5.3.6 (Zend: 2.3.0), fresh install 11-16-2011. Didn't find any mention of this in the FAQ/search of the forum, and of course, the manual we purchased for the Cart is an hour's drive away. :(

We have an item on special (regular price $225, on special for $150 from 2-Jan-2012 to 31-Mar-2012), and that displays as expected in the cart.

When the customer (and now, I) review the item once added to the cart, the price reverts to display the original $225.

I suspect I missed something in creating the special, but haven't been able to figure out why.

A link to the item/cart: http://www.firetrucks4hire.com/pubpool/shoptrolley/index.php?main_page=product_info&cPath=33_34&products_id=196

More curious... created a second item, added a Special, but the behavior is limited only to the first item.

Differences: the "broken" special is on a max quantity of 1 item with the quantity box switched off... though enabling it didn't get it going.

Curious indeed, but at least it's not a systemic issue, just something goofy with a single entry...