Perhaps you have installed the wrong ethernet driver, or didn't install one at all. This can cause internet to go haywire, so i advise you check that out. If you have Windows 7 64 bit right now, installing ethernet driver may not be needed, as Windows 7 installs most basic drivers, but your computer may require a different way for the driver to work, than what Win7 provides. So definitely check the drivers. If the driver is fine, the lan cable may have been damaged since or before the 64 bit system was installed. Try with a different wire, to see if that solves the issue, and if it does, then you know it was the cable itself. If this doesn't solve the issue either, check if the new version of the OS installed a proxy IP to your system...