ArgumentError (dump format error for symbol(0x46)):

Rails 3.1.5
Ruby 1.9.3-p194

log/development.log

ArgumentError (dump format error for symbol(0x46)):
  app/controllers/application_controller.rb:41:in `authorize'

Rendered /home/www/.rvm/gems/ruby-1.9.2-p318@dm/gems/actionpack-3.1.5/lib/action_dispatch/middleware/templates/rescues/_trace.erb (3.3ms)
Rendered /home/www/.rvm/gems/ruby-1.9.2-p318@dm/gems/actionpack-3.1.5/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb (1.1ms)
Rendered /home/www/.rvm/gems/ruby-1.9.2-p318@dm/gems/actionpack-3.1.5/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (6.7ms)

app/controllers/application_controller.rb

 40   def authorize                                                                                                                                                                                                                                                             
 41     if session[:user].nil? then                                                                                                                                                                                                                                             

よくわからない。。。
素直にRails3.2.xにあげたらなおるのかな。