ActionController::InvalidAuthenticityToken (ActionController::InvalidAuthenticityToken):

Error: ActionController::InvalidAuthenticityToken (ActionController::InvalidAuthenticityToken):
Solution:
Add session id to the url.

url = url_for(:controller => ‘documents’, :action => ‘create’, “#{session_key_name}” => cookies[session_key_name] )

$(‘<%= field_name %>’).uploadify({ uploader : ‘/javascripts/uploadify/uploadify.swf’, script : ‘<%= url %>’,