content taxonomy error aborts migration

migrating a content_taxonomy field appears to have partially worked but produced this error:
An AJAX HTTP error occurred. HTTP Result Code: 500 Debugging information follows. Path: /batch?id=441&op=do StatusText: Service unavailable (with message) ResponseText: PDOException: SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'tid' cannot be null: INSERT INTO {taxonomy_index} (nid, tid, sticky, created) VALUES (:db_insert_placeholder_0, :db_insert_placeholder_1, :db_insert_placeholder_2, :db_insert_placeholder_3); Array ( [:db_insert_placeholder_0] => 228 [:db_insert_placeholder_1] => [:db_insert_placeholder_2] => 0 [:db_insert_placeholder_3] => 1250163612 ) in content_taxonomy_migrate_content_migrate_data_record_alter() (line 59 of /home1/explore8/public_html/2tim/sites/all/modules/content_taxonomy/content_taxonomy_migrate.module).

Advice to other administrators: migrate other CCK fields first, then content_taxonomy separately