We're running Rails 2.3.5, not sure if something changed in there. The problem has to do with some of the stuff in this commit http://github.com/dylanz/i18n_backend_database/commit/e1faa3f384daf26b2809aadfdb4f86569615497f
What I was seeing is the object that was being scanned for interpolation arguments looking something like this:
"'activerecord.errors.messages.record_invalid', :errors=>errors"
and not being able to parse out the fact that it needs an errors option. My regex_fu is limited so I haven't been able to come up with something better.