404 on productpage

-- url of the page with the problem -- : mieten.erlebnismanager.info/mietwaren/dekoration
-- HikaShop version -- : 2.3.2
-- Joomla version -- : 2.5.22
-- PHP version -- : 5.3.18-nmm1
-- Browser(s) name and version -- : Firefox 31
-- Error-message(debug-mod must be tuned on) -- : Beitrag nicht gefunden

Call stack
# Function Location
1 JSite->dispatch() /www/htdocs/.../index.php:42
2 JComponentHelper::renderComponent() /www/htdocs/.../includes/application.php:194
3 JComponentHelper::executeComponent() //www/htdocs/.../libraries/joomla/application/component/helper.php:348
4 require_once() /www/htdocs/.../libraries/joomla/application/component/helper.php:380
5 JController->execute() /www/htdocs/.../components/com_content/content.php:16
6 ContentController->display() /www/htdocs/.../libraries/joomla/application/component/controller.php:761
7 JController->display() /www/htdocs/.../components/com_content/controller.php:74
8 ContentViewArticle->display() /www/htdocs/.../libraries/joomla/application/component/controller.php:722
9 JView->get() /www/htdocs/.../components/com_content/views/article/view.html.php:32
10 ContentModelArticle->getItem() /www/htdocs/.../libraries/joomla/application/component/view.php:386
11 JError::raiseError() /www/htdocs/.../components/com_content/models/article.php:178
12 JError::raise() /www/htdocs/.../libraries/joomla/error/error.php:251

Hi,
if got a problem with the product listing. As you can see via the link, there are in the main menü some 1st level subcatgeories and when you click to one, there are also 2nd level subs. The link directly shows the 2nd level subs, what also works fine. In the first Menue item "Mietwaren" I've had the problem that it shows the subcategories twice. So I tried around and eleminated that issue. Later on I recognized, that the prouct listing shows an 404 error. So I disabled sef to have a look, if the sef urls dont work - but that also didnt make a change. Caching is disabled.

What I'm not sure about, is the sef url... I think during the time, the listing works, those have been shorter. Now they are:
mieten.erlebnismanager.info/hikashop-men...ry/41-kerzenleuchter

Before those changes on the first menue, it worked fine. The changes have been, that I've deaktivated the module, but already reactivated it... .

Any idea what to take care about?

Attached you'll find two screenshot. I hope those are the right ones.

Any idea what's wrong?

Yes - thanks for your help!!!