Displaying Errors with Code 500 as 200 in Rails3

Hi!

We make Facebook-Apps with Rails3.
Facebook do not display Errormessages with a Errorcode 500. So we have
to display what comes as error with Code 200.
I am looking forward to modify an existing Gem called buddy which
makes the Facebook-Stuff.

But I don't know how to do this in Rails3. I think this has something
to do with Actioncontroller::Rescue
But I dont know, what to change.

Greetings from Germany,
Klaus