LoadError with UserMailer in Production Mode?

Getting this error everytime i try to use the UserMailer to send an
email, works in development mode, but not in production.

LoadError (Expected /app/models/user_mailer.rb to define UserMailer):

Any ideas?

Using Rails 2.0.2, the user_mailer.rb does define UserMailer just
doesn't seem to work anymore when running mongrel in production mode.

here's my configs
........

production.rb