Service Pack Internet Connection Gone

I am running a home network with two computers. I
connect to the internet through a cable provider through
a cable modem. I am running McAfee firewall and Norton
anti-virus software. Two weeks ago I loaded XP Service
Pack 2. When I did, I could not connect to my internet
connection. I restored the computer to an earlier date
prior to the Service Pack install, and all was fine
again. I later loaded service pack again, and
encountered the same problem. I disabled the XP firewall
hoping this would solve problem, but it still could not
connect to internet. I once again have restored to an
earlier date and am back online. I am afraid to install
service pack 2 again. Can you advise? send to