OK, this is giving me fits. Is there a proper place to have a forum to discuss this solution?
The problem is that you have the possibility of two asynchronous events returning at different times, each effecting the other. As I have been thinking about it, I actually think my first post is the correct solution, because I also think that the correct thing to do is force the field to have the focus if .autocomplete( "search" ) is called. If it doesn't have the focus, then you can still get the possibility of two menus showing up simultaneously, since the menu will not get a blur event if it doesn't have the focus. To prevent the two menu problem, the user of autocomplete must either make sure he focuses the field before the search, or make sure to manually blur the menu when some other event happens.
A test case is difficult to post, because it relies on a slow json call, and jsFiddle and jsbin don't seem to play nice with json easily.