title: File upload issue in Rails 2.3.5 using paperclip
body: <p>I have a Rails 2.3.5 application which has file upload functionality using paperclip. When I upload a file, the first time everything works fine. But the second time I try I get the following error message:</p>
  
  <pre><code>uninitialized constant ActiveSupport::MessageVerifier::Encoding
  </code></pre>
  
  <p>From the trace it looks like an issue with form_authenticity_token.</p>
  
  <pre><code>&lt;% form_for @import, :html =&gt; {:multipart =&gt; true} do |f| -%&gt;
      &lt;ul&gt;
          &lt;li&gt;&lt;%= f.label :source, "Select a file to import" %&gt;&lt;/li&gt;
          &lt;li&gt;&lt;%= f.file_field :source %&gt;&lt;/li&gt;
  
          &lt;%= submit_tag 'Submit' -%&gt;         
      &lt;/ul&gt;
  &lt;% end -%&gt;
  </code></pre>
  
  <p>If I clear the browser cache, I can get it working again. So I guess this is something related to session/tempfile etc. I just dont know what exactly :)
  Is there something I am missing here?
  Any help is appreciated</p>
  
  <p>Thanks,
  Abhilash</p>