Submit button not working in Ruby/Firefox - ruby-on-rails

Question

I'd like to have a single form that has 2 or more field-set_tags and I'd like to have a single submit button to update the changes for all field_set_tags at once, but that's not working ; if I create a form for each field_set_tag and one submit button per form, it works fine ; anyone can help? my simplified partial view _form.html.erb has the following structure
<%= form_for(#my_form) do |f| %>
<%= field_set_tag "Field Set A" do %>
<div class="field>
<%= f.label :"Configure A" %>
<%= f.check_box :ConfigA %>
<%= f.label :"Login" %>
<%= f.text_field :A_Login, {:size => 12} %>
<%= f.label :"Password" %>
<%= f.password_field :A_Password, {:size => 12} %>
<!-- more Ruby code here -->
</div>
<% end %>
<%= field_set_tag "Field Set B" do %>
<div>
<%= f.label :"Configure B" %>
<%= f.check_box :ConfigB %>
<%= f.label :"Login" %>
<%= f.text_field :B_Login, {:size => 12} %>
<%= f.label :"Password" %>
<%= f.password_field :B_Password, {:size => 12} %>
<!-- more Ruby code here -->
</div>
<% end %>
<div class="actions">
<%= f.submit "Update" %>
</div>
<!-- more field_sets and Ruby code here -->
<% end %>
I also tried this with no luck either
<input type="submit" value="Update" />

Answer 1

My issue was caused by a button I configured as a place holder for future use like this
<div class="field">
<%= button_to "Advanced" %>
</div>
When I removed that button, all worked fine
In a similar way, I configured 2 successive submit buttons like this
<div class="actions">
<%= button_to "Update", :type => "submit" %>
</div>
<div class="actions">
<%= button_to "Update", :type => "submit" %>
</div>
the 1st one does submit but the 2nd one generates this error
Unknown action
The action '4' could not be found for L2CircuitTestsController
2 or more successive "Advanced" buttons cause the same behavior : only the 1st one does the job and the other are eclipsed!