I can go through the booking process on www.oneworld.com for ex-AMM itineraries with first flight on RJ which book through AA but if I try to book ex-KRT I can get to the pricing page but when I click on the book button I keep getting the following:

The following error(s) occured

Our lowest fares are not available for the destination and date requested. Please return to the homepage and click on the ?search by schedule? button to find our most attractive fares. (5685 - 2201)

Any other experiences with this?