For the majority of this site, I had been using databinding to DataLists, using generic lists, and the default syntax:
<%#
DataBinder.Eval(Container.DataItem, "PhotoID") %>
However, when I tried using the same syntax for a FormView in conjunction with a ObjectDataSource, I got the title message. It turned out to be simple to resolve:
<%# Eval("PhotoID") %>
I believe it may have to do with how the data is being retrieved.