jQuery onChange isn't triggering an event when text is entered into a form
<p>I have this simeple jQuery code:</p>

<pre><code>$('#category_name').change(function() 
{
  alert('Handler for .change() called.');
  var category = $("#category_name").val();    
});
</code></pre>

<p>And this form:</p>

<pre><code>    &lt;form id="problem_categories" name="problem_category_form" method="post"&gt;
         &lt;p&gt;
         Category Name: &lt;input type="text" size="50" name="category_name" id="category_name"&gt;&lt;/input&gt;
         &lt;/p&gt;                
         &lt;p&gt;
            &lt;input type="hidden" id="category_problem_id" name="category_problem_id" value="&lt;?php echo $problem_id; ?&gt;" /&gt;

            &lt;span class="error"   id="category_error" style="display:none"&gt; Please Enter Valid Data&lt;/span&gt;
            &lt;span class="success" id="category_success" style="display:none"&gt; Category Added Successfully!&lt;/span&gt;

            &lt;input type="submit" class="button" value="Add Category"&gt;&lt;/input&gt;
         &lt;/p&gt;
    &lt;/form&gt;   
</code></pre>

<p>But for some reason the jQuery does not fire when I enter text into the form field. Here is an example page where this can happen on the bottom right: <a href="http://www.problemio.com/problems/problem.php?problem_id=51" rel="nofollow">http://www.problemio.com/problems/problem.php?problem_id=51</a></p>
