ok, that is making sense now.
I have been confused in the past when I type a URL wrong and virgin "helpfully" send me to a page suggesting other alternatives.
I always wondered how that worked without me having installed any software... duh.
Typing that address in the browser as suggested goes to:
http://advancedsearch.virginmedia.com/subscribers
Now I see there is an option to turn it off...
Having done that (by clicking through a series of pages), ping now works properly again.
thanks to all!
Now I can see what machines really are there without these confusing phantom responses.