Autocomplete plugin inside Tabs inside a Dialog: is this a Bug?

Autocomplete plugin inside Tabs inside a Dialog: is this a Bug?

Hello,

I am using ASP.NET MVC2. I have a jQuery dialog that contains a jQuery Tab plugin with three tabs. Inside the first tab I have a table with some input controls. 

I have tried to use an input HTML control with the autocomplete plugin but when I use this plugin I get the following error in the jQueryUI code as soon as the dialog opens.

Uncaught TypeError: Cannot call method 'zIndex' of undefined 

I am using jquery-ui-1.8.4.

I am reporting the piece of the plugin code and I have marked in bold the line that get the error

  2. this.menu = $( "<ul></ul>" )
  3. .addClass( "ui-autocomplete" )

  5.        ..... these lines have been removed for better readability...  

  7. .menu({

  10.              ..... these lines have been removed for better readability...  

  12. blur: function( event, ui ) {
  13. // don't set the value of the text field if it's already correct
  14. // this prevents moving the cursor unnecessarily
  15. if ( self.menu.element.is(":visible") &&
  16. ( self.element.val() !== self.term ) ) {
  17. self.element.val( self.term );
  18. }
  19. }
  20. })
  21. .zIndex( this.element.zIndex() + 1 )
  22. // workaround for jQuery bug #5781 http://dev.jquery.com/ticket/5781
  23. .css({ top: 0, left: 0 })
  24. .hide()
  25. .data( "menu" );
I have asked for help on the stackoverflow.com web site. You can read here the complete discussion.

Can anybody confirm that is a bug or if I am missing something. Thanks a lot!

Regards
Vincenzo