How to debug this java script error

I am building a sharepoint 2007 application.

I am getting the Object Expected error when I am clicking on any of the sharepoint links. When I start debugging with IE Dev Tool the first error that comes up during the page load is this:

--> Sys.WebForms.PageRequestManager._initialize('ctl00$_PPTPScriptManager', document.getElementById('aspnetForm'));

It says: Sys is undefined.

Then I get:

-->WPSC.WebPartPage.Parts.Register('WPQ1','00000000-0000-0000-0000-    000000000000',document.all.item('WebPartWPQ1'));

WPSC is undefined.

When finally the page is loaded and I am to click on a link, I get this:

Object Expected:

   `<td onmouseover="Menu_HoverStatic(this)" onmouseout="Menu_Unhover(this)"   onkeyup="Menu_Key(this)" id="ctl00_ApplicationListMenuControl1__applicationMenun0"><table cellpadding="0" cellspacing="0" border="0" width="100%">

`

What am I missing?

I think you might have left some JS code which is preventing "core.js" (main js file for sharepoint) and because of this you are getting this error. Have a second look on the js code block you have added in your application.