JQuery :: Selectable Plugin Prevents Click Event?

I've recently started working with jQuery. Using v1.3.1 and UI v1.6RC6. I created an accordion with another accordion nested within it. I've set both to selectable. Things seemed to be working fine until I noticed that IE and FF were behaving differently. IE allowed me to open the accordion tab that contained the nested accordion, and then allowed me to open up the nested accordion. In FF, I could not open the nested accordion. I managed to get it working in FF by setting the cancel property to li element (which contained the nested accordion). Questions:

1) I traced through the code and didn't see where jQuery unbound the click event that should have been caught by the accordion headers. The only thing that I can see is that the selectable items catch the mousedown event, and when caught create a helper div element at the same position that the mousedown occurred and at z-index 100. I've read elsewhere that a browser registers a click only if the mousedown and mouseup occurred on the same element. Does adding this element fool the browser into thinking there wasn't a click?

2) Following #1. I've read that event bubbling follows the DOM hierarchy - from child to parent, However, is it correct to assume that the target element initially determined by the element with the highest z-index (assuming all different)? Once triggered then event would bubble up ignoring z-index?

3) If #1 and #2 are fairly accurate, does anyone have any idea why IE would seem to still register a click event? Maybe it ignores the fact that another element with a higher z-indez was added and simply compares mousedown/up coordinates?