For the life of me I cannot figure this out. The jQueryUI tooltip feature (relatively new) works perfectly on absolutely everything, in every browser. Except select boxes in IE! It seems for some reasons that IE is reading every "option" element as a very relevant part of the "select". Thus, while the tooltip works perfect even in IE when you merely hover over a select box, it breaks as soon as you click it.
I am using jQuery version 1.5 beta1 (though I have tested this in every version from 1.4 onward), and jQueryUI version 1.8.8.
Edit: An example of this may be seen at this location.
Here is a link to the bug: http://bugs.jqueryui.com/ticket/8798
The solution they suggest is just wrap the text in another element, for example a div, that will trigger the tooltip.
<div class="tooltip" title="Some text">
<select>
<option>...</option>
</select>
</div>