Why is the help updatewar.jsp not recognizing and loading site.xml of the clm401 updatesite file?

I did exactly what is described in the Infocenter to install local help.
But the updatewar.jsp is not loading my updatesite. Neither if I have site.xml local nor remote.
I also read through many forum articles but I have not found others with the same issue.

I'm running Windows 2008-R2/64bit with WAS 8005/64bit and CLM401.

My steps:
a) define "127.0.0.1  localhost" in etc/hosts
b) disable the remote help with
https://localhost:9443/clmhelp/remote/remotehelp.jsp
c) download the siteupdate from
http://download.boulder.ibm.com/ibmdl/pub/software/rationalsdp/documentation/updatesites/
d) start
https://localhost:9443/clmhelp/updater/updatewar.jsp
e) remove installed content
f) <add> local site, browse to site.xml, give a name "CLM401Local", <OK>

-->> the three blue bars are running for 10-20 seconds
-->> Site List folder remains empty

g) Then I created a Webfolder for the updatesite. I can browse this folder in the Browser and see the files.
h) <add> remote site, give URL to site.xml, give a name <ok>
-->> the three blue bars are running for 10-20 seconds
-->> the Site List folder has now a subfolder with my name
f) open the subfolder, select the Help content, <Install>

-->> It opens shortly the Update Window with the progress bar but the it fails with
-->> PopUp: "Failed to install feature: No repository found at https://bt-clmserver01.company.com/LocalHelpUpdateSites/CLM401updateSite/."

Has anybody an idea what I can do so one of the this method is loading the content?