I've tried a veriety of jQuery plugins recently and I keep getting this error …

… regardless of what plugin I try to use.

I've checked the links to the JS files which are all there and working fine. I'm using Drupal if that makes any difference.

I've run the plugins away from the main site to demonstrate that they are working and that I am doing things right with 100% success.

Any ideas?

Update:

My jQuery file called in the footer:

$(document).ready(function() {          

$('#footer_holder').hide();

// Fancy Box
$("a.fancybox").fancybox({
    'hideOnContentClick': true,
    'titlePosition' : 'over',
    'transitionIn'  :   'elastic',
    'transitionOut' :   'elastic',
    'speedIn'       :   600, 
    'speedOut'      :   200, 
    'overlayShow'   :   false,
});

$("#homepage_slider").easySlider({
    auto: true, 
    continuous: true,
});

});

*note - fancy box works fine. jQuery is sorted out by Drupal. I'm running version 1.4