Several users have reported an issue in which Windows 7 Internet (network) connections die or drop out randomly during routine use. This can cause Web browsers to suddenly stop loading pages; network drives to disappear; and other network-enabled applications to lose functionality. The problem may be especially prominent with the Atheros L1 Gigabit Ethernet 10/100/1000Base-T Controller used on Asus p5k motherboards. There are two potential fixes for this issue:
Install a new driver This driver (FTP Link), intended for Windows Vista, has been reported to solve this issue under Windows 7 in a variety of cases.
Use a new network card Unfortunately, if the aforementioned fix does not work, you may need to use a different network card (NIC). The Dynex DX-PCIGB, available for roughly $30 from Best Buy, has been reported to work well under Windows 7.