We have had several instances where a Vista PC or a Server 2008 machine has been connected to a network and despite picking up an IP address from DHCP has failed to go online and sometimes even failed to communicate with the rest of the network. When checking ipconfig the primary address for the default gateway reads 0.0.0.0 which is only relevant when using dial up networking. The secondary address in the list is the correct one.
So how do you remove the 0.0.0.0 entry for the default gateway address?
Use netsh from the command line to change your network configuration. In this instance open command prompt with elevated privileges and type the following:
netsh interface ipv4 delete address "Local Area Connection"
where X.X.X.X is your local IP address
Now check ipconfig again and the 0.0.0.0 should have disappeared leaving the correct default gateway address.