It looks like this is a problem on IP level.
Possibly some configuration setting has been reset when you installed SP2.
You could check a few things to verify that hypothesis:
– Does ‘ipconfig /all’ show the device with correct
settings for IP address subnet mask, default gateway,
DNS servers, etc.?
– Are the settings for the network interface correct?
are the needed protocols present?
under ‘Internet protocol’:
is the IP address setting correct? (either set by DHCP or
everything manually configured)
(Peer-to-peer over a cross-cable may work, because in that case Windows assigns IP addresses (that are rather strange, but make things work together without configuration), while you don’t need a default gw, etc.)