well it may have changed your IP settings. Please verify that they are the same as before SP2.
also some hardware does have problems functioning.
also you may have to open certain ports to get applications working again.
here is a list of known affected apps with sp2
I had to dig deep to find it (why MS!)
also I would turn the firewall off and just use your router's built in one.
the SP2 firewall also may be conflicting with other firewalls.
please check that site for more info!