Thanks, Ron. I went looking for spaces and found none.
While in dfdm, I noticed the customer had 000 in their Ship To address. I checked and there was no Ship To address for this customer. I removed the 000 from the Ship To field and now it allows a Sales Order to be entered. I went to the SO_ShipToAddress.M4t file and found the customer's 4 ship to addresses were still in the original division. Edited those records to reflect the new division and put 000 back in as the primary and things seem to be OK.
Never would have thought that an unfound ship to address would kill a sales order entry.
John, I looked at both the Partner Portal and InfoSource, but that doesn't mean it's not there. I have a lot to learn about searching. The last four searches I did on the portal for other issues all returned zero articles.