Blank Screen when USPS plugin is published.

-- url of the page with the problem -- : christiangrandparenting.net/bookstore
-- HikaShop version -- : 2.2.2
-- Joomla version -- : 2.5.16
-- PHP version -- : 5.3.27
-- Browser(s) name and version -- : Chrome 30.0.1599.101
-- Error-message(debug-mod must be tuned on) -- :
Notice: Trying to get property of non-object in /home/christia/public_html/cgn/plugins/hikashopshipping/usps/usps.php on line 308
Notice: Trying to get property of non-object in /home/christia/public_html/cgn/plugins/hikashopshipping/usps/usps.php on line 314
Notice: Trying to get property of non-object in /home/christia/public_html/cgn/plugins/hikashopshipping/usps/usps.php on line 314
Fatal error: Call to a member function xpath() on a non-object in /home/christia/public_html/cgn/plugins/hikashopshipping/usps/usps.php on line 366

This was working as recently as Nov. 5 (5 days ago) which was our last order. When going to checkout, we get a blank page, turning debugging on revealed above errors. I've unpublished the USPS plugin for now and reverting to manual shipping method or UPS. The only change to the website since Nov. 5 was upgrade from Joomla 2.5.14 to 2.5.16. No other installs or changes (that I've been told about).

Any suggestions on where I can look next for a solutions.

Thanks.