File Column Field Major issue

Hi All,       I'm using file_column_field for uploading the images it's working fine.But it throws random error as shown below.            eg.,               <%= file_column_field("ad","ad_picture")%>               I'm using like this,but while uploading or editing the image it throws an error randomly:                  undefined method : ad_picture_temp for<Ad:#Object>           i think this issue is comes while creating the file column temporary(temp) object.           It occurs randomly.In single port its working fine,but i configured in multiple port but it throws an error randomly.           Can someone please help on this?           Thanks in Advance.. Regards, Viswanathan.J