Does anyone have a problem with autocomplete? My autocomplete work well with jquery 1.8.3 but can not work with 1.9.0 in Chrome, Firefox (IE still work) ?
Take a look at this jqfaq.com link where the autocomplete works fine even in 1.9.0. And also more questions with answers available there. Hope, this might help you.
The jqfaq link wasn't informative to me on your question, so if you are still pondering, take a look at the new Autocomplete documentation for the source: option.
My hunch (have not tried the code) is that 1.9 somehow tightens the definition of allowed querystrings. Their example would suggest source: "atcomplete.php?term=contact",