[Dbix-class] Empty inserts with add_to_... and create

[apv]

I'm getting a weird error when trying to create() or add_to_...(). I've 
checked my args and such, sorry no code right now, but the underlying 
stuff seems sound and is working in relational find() or manual INSERTs 
with the identical args. It seems like the args are not even getting 
passed through to create(). new() works but insert() or create() or 
add_to...() die with this message:

DBD::mysql::st execute failed: Cannot add or update a child row: a 
foreign key constraint fails [for Statement "INSERT INTO chapter () 
VALUES ()"] at 
/usr/local/lib/perl5/site_perl/5.8.2/DBIx/Class/Storage/DBI.pm line 187.

Does this ring a bell with anyone?

-Ashley