it would be a good practice to predefine the "source" property of the autocomplete (jquery.ui.autocomplete.js ver. 1.8.1) plugin.

I solved this in this way:

file: jquery.ui.autocomplete.js

line (can be some other): 163

code start

source: null,

code end

when you add this, you won't have the error "this.source is undefined on line 201 in jquery..."

first invoker in my case was the _search function of the autocomplete so I've added this to have the function predefined

"source" is also defined in _initSource and it seems that sometimes other functions can't catch up with _initSource and there's a failure