THe LAN is broken mostly in Vista... or so I've been told.

I dunno. It is a BETA.... don't forget that.

And you could try renewing or releasing the IP.. YOu could try uninstalling and reinstalling the NIC.

You could try setting the IP info manually in the NIC properties.

Also you could use your XP network setup wizard to create a configuration disk. Then boot into Longhorn and try to use that disk to setup your networking in Longhorn... but there is not guarantee that that will work.