This post will help you resolve problems with Error Code 0x80070424 in Windows Firewall, Microsoft Update & Windows Defender in Windows 8 | 7.

You will have to:

  1. Run the Windows Update Troubleshooter
  2. Run the Fix-it to restart necessary services and register additional DLLs
  3. Restart Windows Services
  4. Download and install the Windows Update Agent
  5. Reinstall Automatic Updates on a computer that is running Windows XP SP2
  6. Run the Windows Firewall Fix it.

Details at KB968002.