This is worth a try and only takes minutes:
Repair the Windows 8/7/Vista TCP/IP Stack
If you’ve tried everything you can think of to cure an Internet connection problem without success, it could well mean that Windows TCP/IP parameters have become corrupt. This often happens when a virus has been removed from your system but left behind some damage. It can also happen when you remove security software such as a firewall, which is deeply integrated with the Windows networking system.
To fix the problem you need to reset the Windows networking stack. Fortunately Windows 8/7/Vista comes with a built-in tool you can use to do this:
Click Start > All Programs > Accessories, right-click on Command Prompt and choose Run as administrator. Windows 8 users press [Windows Key] + [X] and select Command Prompt (Admin). At the command prompt type: netsh winsock reset catalog and press [Enter]. Next type: netsh int ip reset reset.log and press [Enter]. Restart your PC for the changes to take effect.