AJAX-safe for solid surfaces and Safari

While working on some code today I decided to use Ajax for one of the searches. It is nothing major, just a basic search that returns the matching results from the db as you type in the search params (the js is kicked off on the onKeyUp event). One thing I was surprised to find is Safari seemed to handle it all better than Firefox. They both worked ok for the most part, I just found that if I typed fast, Firefox sometimes seemed to get confused and even locked up one time while Safari handled it all very well. It didn't work at all in IE 5.2 but who cares about IE 5.2.....right?