I have the same issue. We have 7 rows in a grid. 6 require the response. The 7th row is "other, specify" and the response is not required. If they do check the radio button and do not fill in the "other, specify" field, we have java script to ask them to fill that in. But there is always the chance they accidentally checked a radio button and need to uncheck it.
Is there java script so that if they check it a second time it unchecks?