Assuming that the Local Area Connection property sheet is configured to use the correct NIC and that you have found no TCP/IP misconfiuration or corrected it. the next step is to open a command Start -> run -> type cmd. at the prompt type ipconfig /release then when you get a new command prompt type ipconfig /renew. Or you can click the Local area connection icon in the sytem tray and click repair or you can just reboot. This should re-establish the connection.
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