This was previously reported 'fixed' in jquery 1.4: http://bugs.jquery.com/ticket/5514 but seems to have regressed.

Given the following code:

$('a#id').bind('mouseenter', function() {
    aler('bar');
});

JSFiddle: http://jsfiddle.net/3X2tg/6/

When triggering the 'mouseenter' event, no error message is printed to console. It appears the exception is being simply being swallowed here:

// Checks if an event happened on an element within another element
// Used in jQuery.event.special.mouseenter and mouseleave handlers
var withinElement = function( event ) {
	// Check if mouse(over|out) are still within the same parent element
	var parent = event.relatedTarget;

	// set the correct event type
	event.type = event.data;

	// Firefox sometimes assigns relatedTarget a XUL element
	// which we cannot access the parentNode property of
	try {

		// Chrome does something similar, the parentNode property
		// can be accessed but is null.
		if ( parent && parent !== document && !parent.parentNode ) {
			return;
		}

		// Traverse up the tree
		while ( parent && parent !== this ) {
			parent = parent.parentNode;
		}

		if ( parent !== this ) {
			// handle event if we actually just moused on to a non sub-element
			jQuery.event.handle.apply( this, arguments );
		}

	// assuming we've left the element since we most likely mousedover a xul element
	} catch(e) { }
}

As detailed in the previous ticket, it appears the apply() call should probably be moved outside of the try/catch block.

Thanks.