About JQuery Tab Custom Selection

Hi,
I have some issues when trying to implement latest version in JQuery Tab.
I have created custom function in Javascript
function Previous()
        {
            var $tabs = $('#tabs > ul').tabs({ fx: { height: 'toggle', opacity: 'toggle', duration: 'normal' }});
            $tabs.tabs("select", 0);
            return false;
        }

        function Next()
        {
            var $tabs = $('#tabs > ul').tabs({ fx: { height: 'toggle', opacity: 'toggle', duration: 'normal' }});
            $tabs.tabs("select", 1);
            return false;
        }
I have two tabs.
First is tab A, and Second is tab B
The problem with the function is the animation was not shown properly in Mozilla Firefox when you call each of javascript function above but it works well in IE 7.0.

I'm using Mozilla 3.0.6
Any idea to solve this problem?
I'm currently new in JQuery.
Thanks.<br clear="all">
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Best Regards,
N3T