Possibility One:
The problem can be caused by having an invalid or unreachable Preferred DNS server address in the Internet Protocol (TCP/IP) Properties.
To fix this problem:
1. Use Control Panel / Network Connections to right-click Local Area Connection and press Properties.
2. Press Internet Protocol (TCP/IP) and press Properties.
3. Press the Use the following DNS server addresses radial button.
4. Type a valid DNS server IP address into the Preferred DNS server text box.
5. Press OK.
Possibility Two:
If you use a Gigabit Ethernet device, the link status may fluctuate as the NIC driver initializes or negotiates.
Make sure your are running the most current drivers for your network adapter.
You may be able to workaround this problem by disabling media sense.
If disabling media sense does NOT resolve the issue, the only other workaround is to switch to a different NIC.