can you post the full traceback of your error? I have seen some cases where similar errors appear on GAE with list:reference fields, but i don't want to send you on a wild goose chase.
the thing i am thinking of is that on GAE when you have a list:reference the table that you reference must have a format string: db.define_table('dad',Field('name'), format='%(name)s') not sure that it would be at all related here though. cfh