Internal Server Error

-- url of the page with the problem -- : digitalguarddawg.com
-- HikaShop version -- : 2.2.2
-- Joomla version -- : 2.5.16
-- PHP version -- : 5.3.x
-- Browser(s) name and version -- : Chrome/FF
-- Error-message(debug-mod must be tuned on) -- : Internal server error

I had this working perfectly on the development server, now, after uploading to the live server, it crashed after entering the customer details and clicking Next. On further testing, it crashes at almost every point in the shop - adding to cart, proceed to checkout.

I thought it may have been to do with the SSL certificate, so turned off the requirement to use SSL on checkout. I still receive the Internal Server Error.

The live site is under a different URL to the development site, but with the same host. They have been unhelpful.

I'll see if the host will give it to me - I cannot see any logs via FTP.

What are the minimum requirements for running HS? I'm wondering if this server is actually capable of running it.

www.hikashop.com/forum/shipping-methods/...html?start=40#132252

Stupid USPS.... unfortunately, the fix from the thread above does not fix the problem for me.