Missing ActivityParty for converted Activities

Hi,

I got a problem since we've made a conversion from CRM4 to CRM 2011. We have some Activities wich don't have any ActivityParty records of type "Owner". Because of this, when we try to reassign a contact linked with one of these activites from CRM4 to another user, we have this error  : There should be only one owner party for an activity

I tried to run this query, and it returns all the activities without an owner in an activityPartyBase records.

Select * from ActivityPointerBase apb

WHERE  (SELECT 0

           FROM ActivityPartyBase party

           WHERE party.ActivityId = apb.ActivityId

           AND party.ParticipationTypeMask = 9)

I think to make it work again I must insert an activityPartyBase records of type "Owner" (ParticipationTypeMask - 9), but I want to make sure if there is another cleaner solution. I don't like to mess into my CRM Database manually.

thanks!