Rails - Jun 2009 - client side caching problems

Hi guys,

Here is the action I request:

 def index
    @producteurs=Producteur.find(:all)
    last=Producteur.maximum("updated_at").utc
    if stale?(:last_modified=>last)
      ip=request.remote_ip
      @centre=centrage(ip)
      respond_to do |format|
        format.html
      end
    end
  end

for the first request I get a "200 ok" response in firefox
for the second request I get a "304 Not Modified" response in firefox,
GREAT
but for the third request I get a "200 ok" response.  :-(    Nothing
has change in the models.

Any idea why the third request is not a 304?
thanks jef.