This kind of thing doesn't usually happen with a service pack install. I've done them before on production servers with no issues.
- What level of network connectivity do you have?
- Do you have a blinking light on the network card?
- Can you ping the server from an external source?
- Do you have other McAfee software installed HIPS, Firewall?
Have you tried disabling Access Protection and On-Access scanner via the console? Have you tried stopping the McAfee services?
Try these options before you go uninstalling anything.
And have you tried to reboot the server?
Mcafee does have a network filter driver, which normaly gets updated with a Patch (Service Pack). This driver normaly only gets activated after a reboot. If for some reason the old driver had now a problem, this outage could happen. It should be solved after a reboot though. Otherwise it's old/broken LAN drivers.