Uninitialized constant for ActiveRecord model in script/delayed_job, but not rake jobs:work

I'm using Rails 2.3.8 with Ruby 1.8.7. I've made a new ActiveRecord model called Foo (generated using script/generate model Foo ...) with a method #self.bar(x, y) and in a controller I call Foo.send_later(:bar, x, y). On my (Windows) development environment this works fine when I'm running rake jobs:work. On my (Linux) production environment, this also works if I'm running rake jobs:work RAILS_ENV=production, but if i'm running RAILS_ENV=production script/delayed_job start, in the delayed_job.log I get

2011-02-19T12:27:11-0800: * [Worker(delayed_job host:myhost pid:3673)] acquired lock on Foo.bar
Could not load object for job: uninitialized constant Foo
2011-02-19T12:27:11-0800: * [JOB] delayed_job host:myhost pid:3673 completed after 0.0024
2011-02-19T12:27:11-0800: 1 jobs proces开发者_如何学编程sed at 32.4446 j/s, 0 failed ...

My other delayed jobs work fine, only this new one has a problem. Foo is accessible from script/console production, and I've tried touch tmp/restart.txt or even restarting apache2 and then restarting the delayed_job script, but there was no change.

Has anyone seen this problem before?

Use rake jobs:work in a screen session or, less hacky, run it using the god gem or monit so that if the process dies it will be "resurrected".