SSRS 2012 integration SharePoint 2010 - Report Server WMI Provider error: Invalid namespace

I'm using Reporting Services 2012 and SharePoint 2010. I'm trying to use the Reporting Services integration in SharePoint. I followed all the steps which are described by msdn here: http://technet.microsoft.com/en-us/library/gg492276%28SQL.110%29.aspx .

BUT I'm always getting this error "Report Server WMI Provider error: Invalid namespace " when I'm trying to use the Report Server Integration. Yes, I know I have to write it in this way http://<servername>/reportserver . I'm doing so all services are running but I'm always getting this error.

Any help?

Thanks.