I remember a couple of years ago when I was touring Australia and presenting on WSUS I heard about these nasty issues with the WSUS server showing client not yet reported. Ive blogged about it twice before actually here and here.
Well today I can blog a proper solution. In fact Jenelle again showed this to me (probably because I pestered her about and she has never forgotten )
Usually the root cause of the problems is that the Windows Automatic Update client needs to be reset. This tool fixes it!