The computer is connected with ethernet using the Realtek RTL8111E on a Gigabyte GA-Z68X-UD4-B3 motherboard. I had to install Realtek LAN Driver 7.049.0927.2011 to make the networking function at all. It is running Windows 7 Professional 64-bit, with all updates installed.
On bootup, there is no networking. If I wait about a minute, it eventually comes up.
The computer dual boots Ubuntu Precise, which connects to the network with no delay. The DHCP server is dnsmasq on a SheevaPlug running Debian Squeeze. I have double checked that my router's DHCP server is disabled.
I have used Windows very little since the XP days, so I have no idea where to look for diagnostic messages or logs.