Css not rendering the properties correctly after the script call has been made

Border Radius is not supported in IE7-8. Thats why removing it has fixed your problem. You did say, however

Both the accordions were using two different images

So what you could do is put the "curvy corners" on your images instead. Those will show up just as good in IE7 and 8

The important issue is that border-radius is not supported in IE7-8 so that is why it does not show..

On another note, though, you can improve your code a lot by caching references to jQuery result sets..

$('.accordion').live("click", function() {
    var self = $(this); // caching $(this) since it is being used a lot
    self.next('.content-toggle').toggle();
    if ( self.hasClass('section-closed') ){
        self.addClass('section-open');
        self.removeClass('section-closed');
    }
    else
    {
        self.addClass('section-closed');
        self.removeClass('section-open');
    }

    var total = $('.accordion').length;
    var open = 0;
    var faq = $('.faq-accordion'); // caching $('.faq-accordion') since it is being used in a loop 
    for (i=0; i<total; i++) {
        if( faq.eq(i).hasClass('section-open') ){
            open = open + 1;
        }
    }

    if (total != open) {
        $('.show-all').show();
        $('.hide-all').hide();
    }
    else {
        $('.hide-all').show();
        $('.show-all').hide();
    }
});

even better the

    var open = 0;
    var faq = $('.faq-accordion'); // caching $('.faq-accordion') since it is being used in a loop 
    for (i=0; i<total; i++) {
        if( faq.eq(i).hasClass('section-open') ){
            open = open + 1;
        }
    }

could become

var open = $('.faq-accordion:has(.section-open)').length;