This is factually a bug/incompatibility in Safari, but the event normalization done in jQuery can address this issue.

For IE6, IE7, FF and Safari, on a click event, the clientX and clientY values are relative to the top left of the viewport. For Safari 2, they are relative to the top left of the document.

If you scroll down or to the right, the clientX and clientY for Safari is different from all the other browsers.

Sample page here:

http://www.scorpiontechnology.com/cobalt/mouseclick.htm

One fix would be to add this right after the pageX/Y normalization script under the event.fix method:

// Fix clientX/Y for Safari.
if (jQuery.browser.safari) {
	var doc = document.documentElement, body = document.body;
	event.clientX = event.clientX - (doc && doc.scrollLeft || body && body.scrollLeft || 0) + (doc.clientLeft || 0);
	event.clientY = event.clientY - (doc && doc.scrollTop  || body && body.scrollTop  || 0) + (doc.clientLeft || 0);
}

This can be seen working on this page:

http://www.scorpiontechnology.com/cobalt/mouseclick_fix.htm

JK