Not sure if we are dealing with a jQuery implementation of preventDefault or it is the standard JS event.preventDefault() function. In case tha latter is true, it is recommended to change it with a function like this:

function preventDefault(evt) {
    if (evt.preventDefault)
        evt.preventDefault()
    if (evt.stopPropagation)
        evt.stopPropagation()
    return false
}

which will work on older IE versions, too (I think it is needed from IE 8 downwards inclusive): http://msdn.microsoft.com/en-us/library/ie/ff975460(v=vs.85).aspx