New Post: Install this Update.... explanation

As far as i know = AFAIK. ;)

OK, what errormessages you find in Eventlog on the Client? Errormessages in %windir%\WindowsUpdate.log?
The Credentials from you WPP-Login are local admin rights on the clients?

Log on as a local admin, will you find the Update via Windows Update? Is the install manually working?