Forum OpenACS Development: Error when modifing previous response (Survey 5.0.0b8)

I have installed Survey 5.0.0b8. I find this error:

undefined variable `clob_answer'
while executing

"ns_pg_bind dml nsdb0 {

insert into survey_question_responses
(response_id, question_id, clob_answer)
values
(...)"

when I try to modify a previos response in a survey. I couldn't modify it.

Thanks in advance
Cesareo