Hi,

for the start please check if you misconfigured your menu somehow (made it a wrong type), this link should not have anything to do with categories. Other remote possility would be to have the same e.g. content type name and category name and joomla would be confusing the two.

Hi Klas,

i added the Menuitem as "Form" - and selected the Content Type i need. 

The Content Types Name has nothing to do with a category name.

By disabling Joomla Own SEF the link works - but i can´t disable SEF.

I tried to move the link into another Menu and then it works. There might me a bug, but i don´t know which bug :)

Regards, 

Elisa

Joomla SEF uses ALIASES for the categories. There may be some error happening there. Try swapping the aliases around with the menu item that worked and see if it still gives the same error?

Hi,

yes, as WebOnes suggest try chaging aliases of menus, I would say that probably parent of this menu link has the same alias as some category.