JQuery accordion menu / IE7 problem

I’m having an issue with a jQuery script with IE7. The script (adapted from one created by Marco van Hylckama Vlieg) is simple:

function accordionMenu() {
  $('#accordion ul').hide();
  $('#accordion li').click(
    function() {
      var checkElement = $(this).next();
      if((checkElement.is('ul')) && (checkElement.is(':visible'))) {
        return false;
      if((checkElement.is('ul')) && (!checkElement.is(':visible'))) {
        $('#accordion ul:visible').slideUp('normal');
        return false;
$(document).ready(function() {accordionMenu();});

Basically an accordion effect, which can be seen here: beprepared.hillphoenix.com/sessions.html
Click on the italicized text in the main content area.

The only message I see in IE7 is “Error on Page”. Of course, I’m a Mac user, so I have to bother coworkers to check the page on their PCs.

This works fine in every other browser I’ve tested, including IE8. What am I missing? What do I fix?

thanks in advance!

I can confirm that on Vista, it works in IE8 but doesn’t work in compatibility mode (IE7).

Can you please fix the HTML validation errors, and then try again.

Works fine here in IE 7 on Windows XP, 3:49 PM, local time !!

Thanks to both for your help. Will check the validation, and double-check on the OS used by the client in question.