Looks like the missing link is NVidia Chipset mainboards..

I bit the bullet and went the reinstall route, adding all windows
updates upto the begining of November (windows update won't connect
at the moment so can't list the outstanding ones, I think there's 3 or
4, including the Media Center update). Touch wood, we're so far all up
and running ok.

Does anyone have any contact details for someone at MS we can throw
this problem at?