Self-contained demonstration of IE9 fail. Uses Prototype-UJS

index.html.erb

<%= form_tag test_ie_path(0), :method => :put, :remote => true do %>
  <%= submit_tag 'Submit' %>
<% end %>

test_ie_controller.rb

class TestIeController < ApplicationController  
  def index
  end
  
  def update
    respond_to do |wants|
      wants.html { 
        puts '!!HTML!!'
        render :text => 'Epic fail!'
      }
      wants.js {
        puts 'JS'
        render :text => "alert('Full of win');"
      }
    end
  end
end