CBOE: Data Loader shows error message "Object cannot be cast from DBNull to other types"

When importing from an SD file, an error may be returned from the Data Loader log:

"Object cannot be cast from DBNull to other types"

This usually indicates there is a mismatch between the saved mapping being used and the fields that are present in the SDF. Review the fields and sure they match the name and data type of the saved mapping in Data Loader.