The autocomplete extender will only push up content if it is available for the entry you have submitted in the text
This means, that if the autocomplete extender has a target method, either web method or other data source attached to it, which completes a list of "possibilities", according to what you have typed into the textbox.
If nothing happens, it might either be that the ACE is not configured correct, check for java script errors (lower left in IE or Firebug for FF), or that there is a value to auto complete for the entry you have submitted.
Refer to this
Eric
'Not everything is binary, if you look closer you might find some hexadecimal in there somewhere'