FORUM is displayed and then displays the mainpage instead

Hello,

I have a strange behavior with the forums component. The forum shows up in the portal. After a few seconds the forums iView shows the portal homepage top and left navigation in the area of the iView. So I have two times the same header and left side navigation. In the remaining content part (the content part of the inner area) there is a message that says something like "you didn't show a topic or your session expired". When I test the iView it shows the same text and I can see that the forum forwarded to "http://mydomain:myport/irj/portal/forums?ForumsTarget=forums/recent-history.jspa"

We are using the most recent versions of the KMC + forums component.

Has someone an idea what could be wrong with it?

Thx, Vanessa