$.offset is undefined in jquery.ui.position.js

Folks,

I am trying to use the jQuery Dialog widget and have run into a problem. My understanding is that it requires the following:

• jquery.ui.button
• jquery.ui.mouse
• jquery.ui.draggable
• query.ui.resizable
• query.ui.position
• query.ui.dialog

And I add them in my template.php file like this:

  $jQueryUIModules = array();
  $jQueryUIModules[] = 'jquery.ui.button';
  $jQueryUIModules[] = 'jquery.ui.mouse';
  $jQueryUIModules[] = 'jquery.ui.draggable';
  $jQueryUIModules[] = 'jquery.ui.resizable';
  $jQueryUIModules[] = 'jquery.ui.position';
  $jQueryUIModules[] = 'jquery.ui.dialog';

  // Now add the required jQuery files
  jquery_ui_add($jQueryUIModules);

The js files are retrieved, but Firefox throws an error on line 199 of the "position.js" file:

$.offset is undefined

All I'm trying to do is create a button on certain nodes that will popup a little message window (specifically, a replacement for the "Add to cart" button in Ubercart). I figured the easiest way would be to use a little javascript. I must be missing something.

I have verified that all the pertinent js files are version 1.8.2.

Thanks in advance for all suggestions.

/Joel