I am on 8.0.2 and found this error happened for me when I accessed the parent document using notesuiworkplace.editdocument and from this document attempted to open a response document using Formula language, Lotusscript, or from the Create menu…all failed. But if you open the parent document from a view the responses are created ok.
When I opened the PMR they said it was known and being fixed in 8.5 though it didn’t make it into 8.5 beta 2.
Its frustrating, but I need to workaround this using a dozen lines of Lotusscript to get all the fields inherited into the response document rather than a single formula command.