Taking a (working) search url from the browser and adding &format=yaml returns 500. (Worked a few weeks ago.) This also happens if I strip the url down to only the populated field (hostname like)

Processing HostsController#index to yaml (for 10.0.5.128 at 2011-03-07 08:54:01) [GET]
Parameters: {"commit"=>"Go", "format"=>"yaml", "via"=>"fact_values_", "tab_name"=>"", "action"=>"index", "controller"=>"hosts", "search"=>{"name_like"=>"test", "alerts_disabled"=>"0", "puppetclasses_id_eq"=>"", "fact_values_fact_name_id_eq"=>"", "order"=>"", "hostgroup_id_eq"=>""}}

ActiveRecord::MissingAttributeError (missing attribute: hostgroup_id):
app/controllers/hosts_controller.rb:573:in `render_hosts'
app/controllers/hosts_controller.rb:560:in `render_hosts'
app/controllers/hosts_controller.rb:30:in `index'
/usr/lib/ruby/1.8/mongrel.rb:159:in `process_client'
/usr/lib/ruby/1.8/mongrel.rb:158:in `each'
/usr/lib/ruby/1.8/mongrel.rb:158:in `process_client'
/usr/lib/ruby/1.8/mongrel.rb:285:in `run'
/usr/lib/ruby/1.8/mongrel.rb:285:in `initialize'
/usr/lib/ruby/1.8/mongrel.rb:285

Rendering /usr/share/foreman/public/500.html (500 Internal Server Error)