No Network Connectivity on Ethernet Port
You may be unable to achieve network connectivity on an ethernet port. However, wireless LAN and wireless broadband work, and ethernet connectivity works at other locations (ie using different switch/hub hardware).
This could occur if the speed of the network adaptor is set to use a speed which is higher than the speed supported by the switch the machine is connected to. For example, if the speed has been set to 1.0Gbit but the switch is only 100Mbit.
Generally, the speed setting on a network adaptor under Device Manager should be set to Auto, and the network adaptor will automatically negotiate. If it is set to a specific (higher) speed it will not fall back to a lower speed.