Ajax Sort of Working. Model being saved but view not being updated.

I am trying to create a model and update the page element with ajax.
The model is being saved and committed to the database. However the
view just sits there and does nothing. If I refresh the page manually,
the new model is there.

The error log:

ActionView::TemplateError (You have a nil object when you didn't
expect it!
The error occurred while evaluating nil.created_at) on line #4 of
pizzas/_pizza_comment_item.html.erb:
1: <table>
2:
3: <tr>
4: <td class="extend_td_time"><%=
pizza_comment_item.created_at.strftime('%B %d, %Y - %H:%M %p' ) %></

5: <td class="second_td_comment"><%= pizza_comment_item.comment
%></td>
6: </tr>
7:

Controller:

def show
  @user_id = session[:user]
  @user = User.find(@user_id)
  @pizza = Pizza.find(params[:id], :conditions => {:user_id =>
@user_id})
  @pizza_comments = PizzaComment.find(:all, :conditions => {:pizza_id
=> @pizza, :user_id => @user_id}, :order => "created_at DESC")
end

def add_pizza_comment
  @user_id = session[:user]
  @user = User.find(@user_id)

  @pizza_comment = PizzaComment.create!(params[:pizza_comment])
  render :update do |page|
    page.replace_html("pizza_comment", :partial =>
"pizza_comment", :object => @pizza_comment)
  end
end

_pizza_comment_item.html.erb

<table>

<tr>
  <td class="extend_td_time"><%=
pizza_comment_item.created_at.strftime('%B %d, %Y - %H:%M %p' ) %></

  <td class="second_td_comment"><%= pizza_comment_item.comment %></td>
</tr>

</table>

pizza_comment.html.erb

<h3>History</h3>
<div id="show_comment_list">
  <%= render :partial => "pizza_comment_item", :collection =>
@pizza_comments %>
</div>
<p></p>

show.html.erb

  <div id="pizza_comment">
    <%= render(:partial => "pizza_comment", :object => @pizza_comment)%>

  </div>

  <% form_remote_tag :url => { :action => 'add_pizza_comment' } do %>
    <%= text_field 'pizza_comment', 'comment' %>
    <%= hidden_field 'pizza_comment', 'user_id', :value => "1" %>
    <%= hidden_field 'pizza_comment', 'pizza_id', :value => "2"%>
    <%= submit_tag 'Add Comment' %>

  <% end %>

Your add_pizza_comment action renders the pizza_comment partial, which references @pizza_comments. That action doesn't defined @pizza_comments

Fred