3762986 - Estimated Delivery Date "Required for confirmed or back ordered items" order confirmation error

I receive the following error message on the Est. Delivery Date (Estimated Delivery Date) field when creating an order confirmation that is back-ordered against a specific purchase order:

The delivery date is not specified for line item number [x,xx,xxx].

or

The delivery date you entered is outside the range (xxxx-xx-xxTxx:xx:xxZ - xxxx-xx-xxTxx:xx:xxZ) allowed by the buyer for the item xx. 

SAP Business Network

NextGen, Schedule, Reschedule, Restriction, Deadline, Fulfillment, Compliance , KBA , SBN-AN-TX-POA , Transaction (Purchase Orders, Ship Notices & Goods Receipts) , Problem