TCP/IP problems can be exceedingly difficult to troubleshoot, and at times your TCP/IP connection appears to break for no apparent reason. If you have a broken connection, try the following

• Try automated repair
• Right-click the broken connection in the Network Connections folder and choose Repair.
• Run the Network Setup Wizard. It walks you step by step through TCP/IP and network configuration and will correct any errors you might have introduced inadvertently.
• Reset your router. If you have a home network, the problem might lie with the router or in the connection between the router and your broadband provider
• Reset your cable modem or DSL modem. If you have a broadband connection, the problem might lie in the assignment of your IP address by your ISP. Power off your cable modem or DSL modem, unplug its Ethernet cable, and leave it powered off for five minutes. Then restart it. This is also a good time to reset your router. You can also try releasing and renewing after you've turned the connection back on.