Array params in form_tag

Hello i have a lot of time trying to figure this out.
I am having problem sending array params with form_tag :remote=>true

form.erb
  <%#= form_tag reporte_client_reports_path do%>
  <%= form_tag reporte_client_reports_path,:remote=>true do%>
   <p>
     <%= label_tag :cuts %>
     <%= select_tag "cuts[]", options_from_collection_for_select(@cuts,
"real_cut", "cut"), :multiple=>true, :id => "cuts"%>
  </p>

<p>
   <%= submit_tag 'Send' %>
</p>
<%end%>

Controller
def report
      @cuts = params[:cuts]

respond_to do |format|
        format.html {render :layout => false if request.xhr?}
        format.js #{render :layout => false}
  end
end

Results

debug results:
- 2011-02-15,2011-02-28,2011-03-15,2011-03-31

It work if i use
  <%= form_tag reporte_client_reports_path do%>

debug results:

I resolved in functional way, but there might be something very weird
with this in my controller:

if request.xhr?
        @super = params[:supermercados].to_s.split(",")
        @cortess = params[:cortes].to_s.split(",")
        @prods = params[:productos].to_s.split(",")
end