You get this resolved yet? Or are you still bumming off a friend's box?
I've had some peole go through the same symptoms when they've swapped out a switch, router, NIC, or entire PC in their home networks. All the software is set up right, but the hardware needs to reacquire the serials for all the devices. Usually all that needs to be done is to power down the network devices for about 30 seconds, then reboot them. The modem registers the MAC of the router or NIC in your PC, any routers do the same to any switches/hubs/etc. in route back to each of the PC's on the network and then everything is up and running again.
Don't know if it'll solve it, but it's been known to work just about everytime with local DSL and Cable subscribers here.
The few times this hasn't worked it's been because of a failed DNS lookup. There are some viruses out there that over-ride the TCP/IP settings--the first thing they target is the DNS section. If you have the 2 PC icon in the systray representing your Ethernet connection, double click this to get to the network connection properties screen. Otherwise, you can right click the Network Places on your desktop, select "Properties", then double click the icon for your "Local Area Connection". Open the "Properties" page, then scroll down to your TCP/IP listing, and double click it. Confirm the settings with your ISP. Most Cable subscribers will use the automatic settings (Obtain the IP address and DNS server addresses automatically should be checked), while DSL will often have an IP and DNS assigned specifically. You can still list specific DNS entries and obtain your IP automatically. This is where the viruses knacker up your connection. They'll put bogus 192.xxx.xxx.xxx or 169.xxx.xxx.xxx entries in there. You could test it yourself by putting in a new DNS entry in the first position. I'm currently using these in different installations:
22.214.171.124 Bellsouth DNS
126.96.36.199 RoadRunner DNS
188.8.131.52 BTI Telecom DNS
Good Luck PP!
If it ain't broke don't try to fix it! But, hell if you can tweak that bastard just a little bit more....hehehe.