Thanks for the info, Don.
I'm using Crystal Reports 2013, SP 1, version 14.1.1.1036, CR Developer, Full Product.
While I said that I was running VS 2015, I get the same error in VS 2013. The program was actually developed in either 2013 or 2010.
I'm using the Oracle ODBC driver (Oracle in Roaclient11g_home1). This is a 32 bit driver, but the OS is 64 bit. I'm thinking that may be the problem but, as I said, opening and running the report directly in CR works fine.