How can it be possible to get 404 Errors on URLS here in SEOMOZ, but if i try to load them in my Browser they load...

[morepixel]

This post is deleted!

[THB]

When I load up "http://shop.samson.de/index.php/products/hardwarepaket.html" into my browser it returns a 404 page:

404 - Seite nicht gefunden

Leider konnte die angeforderte Seite nicht gefunden werden, scheinbar wurde eine nicht korrekte URL eingegeben. So ist der 404 Fehler entstanden. Bitte nutzen Sie unsere Suche oder wechseln Sie zu unserer Startseite um in unserem umfangreichen Sortiment zu stöbern.

The page might load up, technically, but it's returning a 404 Page Not Found header response, which is why crawlers, like SEOmoz, are displaying it as a page not found.

This is expected, and an acceptable practice, so I would not worry (unless that page is supposed to have content, then you had better check the code for any errors).

[morepixel]

This post is deleted!

[shebinhassan]

I also see the 404 page when I try to load the url that you gave.

[THB]

Both of those URL's you provided return a 404 error.

However, when I do click "English", the page loads up.  And if I visit this URL (which I created myself), the product comes up, too:

http://shop.samson.de/deutsch/products/hardwarepaket.html?___from_store=english

It seems you have some rewrite issues as you already mentioned.