cannot see computers on home network

> - apologies if this gets posted twice -
> I have 3 computers on a home network, Vista Home Premium DT, Vista Home
> Premium LT, and XP Media Center DT. Previously all computers could see
> all
> other computers and share files. Today I installed MS update on the Vista
> machines, and the Vista DT cannot see other computers nor can they see it.
> The Vista LT and XP can see each other. All computers are discoverable
> and
> have shared folders; LLTD is checked.
> I system-restored back on the Vista DT but still am unable to see the
> other
> PCs.
>
> --
> Charlie