Windows Update Troubleshooter
http://v4.windowsupdate.microsoft.com/troubleshoot/

Copies from the above site link.

This error is proxy/firewall related, so double-check your firewall/proxy
settings.  Try disabling your firewall and see if the error persists.
CheckPoint Firewall is one product that is a known culprit of this error.
Make sure that TCP/IP ports 80 and 443 are open in both directions.   Make
sure your firewalls are not blocking scripting functions on web site.  This
error is the result of your PC's inability to connect to a component of the
Windows Update site.  Disable all 3rd party applications (like Anti-Virus
software) before accessing the site.  Here are a few ways to try to resolve
this issue:

Suggestion 1
===========

Check your HOSTS file (it may also be called HOSTS.SAM) and make sure you
don't have any static IP entries for the Windows Update web site listed in
the file.  If you are running Win98/ME, the HOSTS file will be in this
folder:

C:\Windows

If you are running WinNT/2K/XP, it will be in this folder:

C:\WINDOWS\system32\drivers\etc

You can use Notepad to open the HOSTS file.  You may need to "tell" Windows
to use Notepad to open the file.

Applications like web accelerators, TweakMasterDNS, etc. can add static IP
entries for the Windows Update site into your HOSTS file and when this
happens you will get the 0x80072F76 error message.

Suggestion 2
===========

Check your firewall/proxy settings and also try disabling your firewall.
This error is the result of your PC's inability to connect to a component of
the Windows Update site.  Disable all 3rd party applications (including
anti-virus) before accessing the site.

Suggestion 3
===========

You may be able to resolve this issue by adding the following Web sites to
the trusted sites list in Internet Options:

 http://Windowsupdate.microsoft.com
 http://V4.Windowsupdate.microsoft.com
 https://v4.Windowsupdate.microsoft.com (Note: The https is correct)
 http://Download.Windowsupdate.com

To add these web sites to the list, follow these steps:

1. Open Internet Explorer.
2. Click "Tools," and then click "Internet Options."
3. Click "Security."
4. Click the Trusted Sites icon.
5. Click "Sites."
6. Clear the check box "Require server verification (https:)for all sites in
this zone."
7. Add all four sites listed above.

Suggestion 4
===========

This issue may be resolved by adding the Windows Update sites to the
exceptions list in the Internet Options Proxy Settings.
To access the Exceptions settings:

1. Open Internet Explorer
2. Click "Tools" and then click "Internet Options."
3. Click "Connections" and then click "LAN Settings."
4. Click "Advanced" and add windowsupdate.microsoft.com;
v4.windowsupdate.microsoft.com, and download.windowsupdate.com to the
exceptions list.If you run other proxy/firewall software, then add the sites
to the exception list for those applications as well.