Hi Don,
I think the table for 12C extends to the next page of the platform document, and does cover a few more options: ODBC Oracle 12.1, OLEDB Oracle 12.1 and Oracle Native Client 12.1.
However, taking a pragmatic view, I guess there's no immediate fix other than jumping a version or two of Crystal. I'll certainly download and test 2013.
Thanks again for you help.
Stephen.