[web2py] Many to Many TypeError: int() argument must be a string or a number, not 'list'

[johntynan]

I would like to create a many-to-many relationship in the following
model, where many "stories" can appear in many different
"roadtrips" (think songs to mixtapes).

db.define_table(
    'roadtrip',
    Field('name'),
    Field('description', 'text'),
    Field('created_by',default=me,writable=False,readable=False),
 
Field('created_on','datetime',default=request.now,writable=False,readable=False)
    )

db.define_table(
    'story',
    Field('user_id', db.users,readable=False,writable=False),
    Field('roadtrip_id', db.roadtrip),
    Field('story_id', 'integer'),
    Field('title'),
    Field('latitude'),
    Field('longitude'),
    Field('comment', 'text'),
    Field('created_by',default=me,writable=False,readable=False),
 
Field('created_on','datetime',default=request.now,writable=False,readable=False)
    )

db.story.roadtrip_id.requires=IS_IN_DB(db(db.roadtrip.created_by==me),'roadtrip.id','%
(name)s')

I am able to create a multiple-select element on the CRUD form by
simply adding "multiple=True" to this

db.story.roadtrip_id.requires=IS_IN_DB(db(db.roadtrip.created_by==me),'roadtrip.id','%
(name)s', multiple=True)

However, I am receiving the error:

TypeError: int() argument must be a string or a number, not 'list'

I posted the traceback here: http://pastie.textmate.org/1187996

(as an aside, is there a better way to post a traceback that is more
readable, should I just copy/paste from the html error page, as
opposed to the logged file under errors?)