Registering contact for a free event - fatal error "Field 'fee_currency' doesn't have a default value"

This error happens during back-office registration of participant for a free event (civicrm/participant/add?reset=1&action=add&context=standalone&eid=1)
We need to either set a default value of NULL for participant.fee_currency or PASS in NULL when inserting participant record for FREE events.

INSERT INTO civicrm_participant (contact_id , event_id , status_id , role_id , register_date , source ) VALUES ( 2 , 1 , 1 , 1 , 20100917125200 , NULL ) [nativecode=1364 ** Field 'fee_currency' doesn't have a default value]
[type] => DB_Error

NOTE: This site only had civicrm_data.mysql loaded (not generated ) - so there was only one event. AND I accessed the registration page via Event Links button under Configure Event (note the eid=1 in the querystring above).