Hmm, none of the jQuery events for OPC are "firing"; changes to the shipping-method don't result in the AJAX call to change the shipping cost and changes to the payment method don't cause the payment-type/submit-button display to be invoked.
What I see in the FireFox console:
setFormSubmitButton, payment-module: null index.php:191:13
Showing "confirm" index.php:191:13
Setting orderConfirmed (0), submitter (null) index.php:191:13
jQuery version: 1.12.0 index.php:191:13
window.controllers is deprecated. Do not use it for UA detection. index.php
In the Chrome console:
index.php:25 A Parser-blocking, cross site (i.e. different eTLD+1) script, https://code.jquery.com/jquery-1.12.0.min.js, is invoked via document.write. The network request for this script MAY be blocked by the browser in this or a future page load due to poor network connectivity. If blocked in this page load, it will be confirmed in a subsequent console message.See https://www.chromestatus.com/feature/5718547946799104 for more details.
index.php:956 A Parser-blocking, cross site (i.e. different eTLD+1) script, https://ssl.google-analytics.com/ga.js, is invoked via document.write. The network request for this script MAY be blocked by the browser in this or a future page load due to poor network connectivity. If blocked in this page load, it will be confirmed in a subsequent console message.See https://www.chromestatus.com/feature/5718547946799104 for more details.
(anonymous) @ index.php?main_page=checkout_one:956
index.php:191 setFormSubmitButton, payment-module: null
index.php:191 Showing "confirm"
index.php:191 Setting orderConfirmed (0), submitter (null)
index.php:191 jQuery version: 1.12.0
None of the OPC's jQuery events are firing. You *should *see console logs when the shipping-method and/or payment-method are changed, but I'm seeing nothing after the OPC's initial load. I'll continue investigating, but wanted to report back to let you and others know what's going on.