Unidentified Network - Local Access Only

I have been using Vista since the first day it came out, on a wireless
network connected to a pc using xp with absolutely no problems at all. A few
days ago (same day onecare did a major update - coincidence?) I started to
get unidentified Network coming up on my network connection, local access
only. Looking and the information I had 2 networks showing at the same time,
both set to public.
I managed to delete one, and put the other back to private which seemed to
work for a time, but then after a while reset itself to unidentified network
again.
I have updated firmware, reinstalled software all that seems to work
(several occasions) , until a while later when it resets again to
unidentified network. Sometimes showing 2 networks rather than one.
Sometimes when I seemed to have fixed the problem with the vista computer,
the xp then cannot find the network. This problem is drivings me nuts.
Everytime I think I've solved the issues, the next day things are back to
unidentified network - local access only. I can plug my vista computer into
the modem, but that means my xp computer can't access the internet.
Just seems strange a lot of people are having the same problem all of a
sudden.
Is it down to a vista or onecare update?
Many thanks,
Alan.