XC buttons are one of the hardest thing to make work properly with other elements. The way they are designed is just ridiculous. Once you add href it changes completelly the whole button structure and uses different classes. If you change these classes it will throw off other buttons
it's fun isn't it. What you can do is copy most of the css applying to it under new classes, use them for this one button and change them so the button sits properly. You can add the new classes as additional_button_class="xxxxx". Use Firebug, it's a must here