I've been receiving a similar error (different line no). However in my case, I'm not sure its due to a constraint violation as I've double and triple checked the values being passed into the new object.

Can't call method "resolve" on an undefined value at /usr/local/share/perl/5.8.8/DBIx/Class/Row.pm line 723.

I'm still investigating this and will let you know if I figure it out.