NIS kills connectivity
Compaq AMD 3800 running Vista Home Premium lost connectivity. The box would not acquire a DHCP address but would only default to a Windows 169 address. I suspected Norton Internet Security. Turning off NIS did not fix the problem. In fact I found it impossible to turn off the Anti-Scam portion of the software.
Uninstalling NIS fixed the problem.
I replaced the functionality with AVG free and Windows Defender.