jQuery / "'Sys' is undefined"

Hi.  I am trying to use some way-cool jQuery alerts in my ASP.NET website.

One of the first alert() calls that I'm going to want to eliminate is actually called from my Page_Render() event on the server side.  It's a browser warning about IE.

After referencing this jQuery tool's js/css files and trying my app out in IE (so that it executes the RegisterClientScript() call that adds the new JS), I get this

'Sys' is undefined

error.  It happens in this part of the page's execution:

      $(document).ready(function() {
         Sys.Application.add_load(function() { Page_onLoad(); });
      });

Does not happen in Firefox...but then, remember, it's the server-side script registration that's bombing out with the new jQuery alert() tool.  

This same server-side code does not fail with the old conventional alert() call.

Now, here's the deal.  I can use Google, and there are tons and tons of "here's how to fix this problem" sites on the net that deal with this specific error.

I CAN comb through those, and I AM combing through those now.  But I'm posting this question in an attempt to find someone who has dealt with this particular error and has specific knowledge or experience with it to help me out.

I repeat:  I can use Google, and AM using Google, so please don't just send me links.  I've tried tons and tons of "fixes", and am STILL trying them.  None have worked.  Please--I need someone with knowledge/experience specific to this problem.

Thank you!  Happy to post web.config markup, or whatever, if that helps.