Repair TCP/IP stack is necessary at times because the links between the layers may become broken. When you try to ping an address and receive a response but your computer still unable to connect to your network or the internet.
Start, Programs\Accessories and right click on Command Prompt, select "Run as Administrator" to open a command prompt.
Reset WINSOCK entries to installation defaults: netsh winsock reset catalog
Reset IPv4 TCP/IP stack to installation defaults. netsh int ipv4 reset reset.log
Reset IPv6 TCP/IP stack to installation defaults. netsh int ipv6 reset reset.log
Reboot the machine.
