The way that the Global Distribution System (GDS) system works is that fares are held in "cache" that reflect the last update given to Orbitz. When the Orbitz computer goes to ticket, it requests the ticket at that price. Delta rejected the request because that fare is no longer available. Thus you were given 24 hours notice.

9 out of 10 times, Orbitz will force Delta to honor the fare that was held in cache.

I would hold tight. I had this happen and purposefully booked on Orbitz. I waited and was given a confirmation within 24 hours.