Error when clicking on specific order in backend

Suddenly an error appeared in the backend when clicking on a specific order number in the order-view in the bacend. Instead of viewing the order detalis, I get this page when using Google Chrome:

When using Firefox I just get a blank screen, and with IE i get:

The website cannot display the page
HTTP 500
Most likely causes:
•The website is under maintenance.
•The website has a programming error.

The problem was still there after updating Joomla to ver. 2.7 and I have the lates Hikashop Business installed.

Problem solved! To others experiencing white screens or "HTTP Error 500", try this: Turn on the "Debug System" on Global Configuration in Joomla. Then the error-message may point you directly to the solution, at least it did for me