In the DocuWare Setup the available websites in IIS cannot be retrieved.
You'll get following error message:
 The object identifier does not represent a valid object. (Exception from HRESULT: 0x800710D8)

If there is a web site in IIS, which has only a FTP binding resp. no HTTP binding, the web sites cannot be retrieved by DocuWare Setup. Therefore temporarely add a HTTP binding to the appropriate web site in IIS.
After the installation you can delete the binding again.