Had this problem recently, and fixed it by resetting winsock (I think this only works for Windows 7 and above)
Open CMD as admin
you can get at that from the start button (right click in Windows 8.1)
Type
netsh winsock reset
and hit RETURN
Restart computer
It worked for me, anyway, but YMMV!
This link gives more details
forum.thewindowsclub.com/.../35087-reset-winsock-windows-7-8-a.htm.