Fatal error after updating joomla and hikashop

-- HikaShop version -- : 2.3.5
-- Joomla version -- : 3.4.0
-- PHP version -- : 5.4.37
-- Browser(s) name and version -- : Firefox 36.0
-- Error-message(debug-mod must be tuned on) -- : Fatal error: Call to a member function hashPassword() on a non-object in /home/httpd/vhosts/pazifiklachs.ch/httpdocs/libraries/joomla/user/user.php on line 617

// Line 617: $array = $this->userHelper->hashPassword($array);

Hi there,
I updated both joomla and hikashop today, and received the error message mentioned above when I checked, if everything was still working. First, I selected products, proceeded to checkout, registered as a new customer, typed enter—and received that error message.
Could you please give me a hint what to do?
Many thanks in advance.

Did you ever resolve this? I've got the same issue after upgrading to J! 3.4.0. I saw the response on your thread on the Joomla forum: forum.joomla.org/viewtopic.php?f=715&t=875148 but am not sure how that fix would be applied to HikaShop. I also upgraded from HikaShop 2.3.5 to 2.4.0 in hopes that it would resolve the problem, but no luck.

It failed for three days, then it ran smoothly again for whatever reasons.
I didn’t change anything anywhere; the only reply I received in the joomla
forum was to cryptical and for me and written according to the principle of hope.

Ok, I'm thinking this might be a caching issue in the browser. I use Chrome as my primary browser. After updating all components, etc. I was still getting the error in Chrome. However switching to Safari, everything worked fine. An incognito window in Chrome also worked fine, so that might explain why you had problems for three days and then it worked again. Either way, I'm considering this resolved.

Well, I tried Chrome and Safari as well. And I’ve never done it before for this website. A caching issue would surprise me. Anyway, I’m considering it resolved, too.