Nested routes problems

Hi i am using nested resources in my application like this

  map.resources :forums do |forum|     forum.resources :topics do |topic|       topic.resources :posts     end   end

while i am submitting a from with url like this http://localhost:3000/forums/1/topics/new

i am facing the problem

"Only get, put, and delete requests are allowed."

Please help me

map.resources will map http://localhost:3000/forums/1/topics/new to a GET request. Your form should be posting to http://localhost:3000/forums/1/topics/.