Production version skips validation

I'm trying to validate_presence_of a hidden_field, which works fine on my machine, but when I upload it to the production server (Apache front-end running WEBrick behind) it skips validation every time. The form field values are assigned with a javascript function, and then it is submitted using javascript instead of a submit tag.

Controller:   def result   case @request.method       when :post         @result = Result.new(@params['result'])         if @result.save           flash['notice'] = "Evaluation Submitted"           redirect_back_or_default :action => "nextpt"         end       when :get         @result = Result.new     end   end

View:

                            <%= start_form_tag :action=> "result" %>                             <%= hidden_field "result", "DefinitionUseful" %>               <%= hidden_field 'result', 'DefinitionComments' %>                             <%= hidden_field "result", "SOPPUseful" %>               <%= hidden_field 'result', 'SOPPComments' %>                 <%= hidden_field "result", "RIDeMResultUseful" %>               <%= hidden_field 'result', 'RIDeMResultComments' %>               <%= hidden_field 'result', 'EvaluatorUserID', :value=> session['user'].UserID %>                             <%= hidden_field 'result', 'StudyPatientNumber', :value=>@patient.PatientNumber %>                 <%= end_form_tag %>

          <tr><td colspan="3" align="center"><input type="button" value="Submit and Continue" onclick="submitForm();" /></td></tr>

Model: class Result < ActiveRecord::Base   set_table_name "CCStudyResults"

  validates_length_of :DefinitionUseful, :minimum => 5, :message => "seems to short" end

I'm still pretty new at this. Any ideas? Thanks!!!