Cannot get simple PopupControlExtender to work.

I am about as confused as I can get. I am relatively new to asp.net (VB.net code behind) but this is giving me far more grief than it should be. All I want to do is have a button display a small window with some text in it for the user to read. 

<div id="leftColumn"><asp:Button ID="Button1" runat="server" Text="Click For Window"  /><asp:Panel ID="Panel1" runat="server" CssClass="popupControl"><p>TEST Stuff. Lorem Ipsum textum fillum spaceum.</p></asp:Panel><asp:PopupControlExtender ID="PopupControlExtender1" runat="server"
      TargetControlID="Button1"
      PopupControlID="Panel1"  ></asp:PopupControlExtender></div>

The css file contains "visibility:hidden;" for Panel1. I run the page, and click the button and get nothing. I also tried in-line with visible="false" with a codebehind that on click, changes to Visible=true. Have also tried "display:none" in-line with Panel1 with no code behind. 

Absolutely nothing works. At this point, I think it is a setting. I did a debug and saw something that said it could not find the source code for the popup but if that were the case, wouldn't I not be able to add AJAX at all? 

I do have a script manager on the page (from the master page).