Apologies for the stream of replies, but not sure when anyone will read them, and getting all facts on the table.
So then tried doing away with the RadBarcode tag on the page entirely, and tried using it in server-side code instead as detailed at http://www.telerik.com/help/aspnet-ajax/barcode-outputtype.html
. Added a RadBinaryImage tag in its place. Then server code creates an instance of RadBarCode and attempts to use GetImage() to save it to a stream which is applied to the RadBinaryImage.dataValue property. But the 2012 Q3 version of RadBarcode has no GetImage() method, so this is a wash too. Can you tell me the earliest version that DOES support GetImage()? We are unable to upgrade all the way to the 2014 version as there are numerious site breaking issues for us that we don't have time to resolve at this time.