I will keep this post short since it’s a fairly simple answer:
SharePoint uses the $() namespace in specific instances – one of these can be seen in the FAST Search Center and only in specific areas and page states. When jQuery is called in the FAST Search center and jQuery.noConflict(); is not present, jQuery will mess with SharePoint’s $() and cause errors to pop up on the page.
The testing I did was a while back, so I don’t have a specific example or screenshots to share, but I know we spent hours troubleshooting until we found the culprit.
How it works
You add the line
jQuery.noConflict();
to the top of your JavaScript block. Then you replace all occurences of $(…) with jQuery(…) in your code (like the example below).
Instead of:
$(document).ready(function() {
$('#buttonElement').click(function() {
alert('Button Clicked');
});
});
Use:
jQuery.noConflict();
jQuery(document).ready(function() {
jQuery('#buttonElement').click(function() {
alert('Button Clicked');
});
});
You can read more about the function on jQuery’s site.
I hope you found this helpful

[...] Putting jQuery into noConflict mode [...]