Cart freezing up

I am working on a website for a customer. During checkout process, it gets to the payment page to select payment method and shipping method. When you click continue, nothing happens. The button does not initiate an action to go to the next page.

Any thoughts on why this would be?



jquery issues, especially if you have a third-party modification

Similar problem - on two of the three catalogue formats - image matrix, and image&details list, adding to the cart freezes with the loading popup rolling - forced refreshing the page shows that the cart has updated and restore the page to an active state. The third grid style catalogue display works fine, and updates the cart, shows the successful update popup, and returns.

Any ideas???