First, are you aware that whenever you change the device connected directly to a cable modem that you have to do a complete reset of the entire network every time you change the device connected to the modem?  To do this, shut everything down.  Wait 5 minutes.  Turn on the cable modem.  Wait another 5 minutes.  Then turn on the device connected directly to the modem (either a router or a computer).  Finally, if you now have the connection to the router, turn on the computers connected to the router.

 

If this is not the problem, check to see if the ethernet network adapter appears in Device Manager and shows no problems.  If it isn't there or shows problems, install the drivers for the network adapter. 

 

Steve

I had the same issue with my Inspiron 1150 laptop.  To solve issue I had to delete the winsock and winsock 2 from the registry and re-install tcpip.  I have attached the link from Microsoft to resolve issue.

You have to scroll down aways, but you need to delete two keys, reboot and
then add the TCP/IP protocol back.  Have to boot twice.

http://support.microsoft.com/default.aspx?scid=kb;en-us;811259