0x800A138F Windows Update Error
If you have received this error when trying to run windows update, there are four major reasons/causes for this 0x800A138F error. The possible fixes and solutions are also listed.

0x800A138F error/cause 1
The date or time on the computer is wrong.
0x800A138F error/cause 2
IE (Internet Exporer) does not allow for the redirection of CGI (Common Gateway Interface)information to an SSL server when coming from a non-SSL server.
0x800A138F error/cause 3
Neither SSL 2.0 or SSL 3.0 have been enabled in IE (Internet Explorer).
0x800A138F error/cause 4
English is not set to be the preferred language.

Here's how to fix each of the above errors.

0x800A138F fix/resolution 1
Go to the machines control panel (under the start menu) and set the date/time through the "Date/Time" icon.
0x800A138F fix/resolution 2
Make sure that the proxy settings are correct in IE (Internet Explorer) under Tools / Internet Options / Connections
Also on the tools menu, click Internet Options / Advanced (tab). Then make certain "Use HTTP 1.1" is selected. Also and "Use HTTP 1.1 through proxy connections" is selected.
0x800A138F fix/resolution 3
Go to the Control Panel and open the Internet icon. (Or on the Tools menu in IE click "Internet Options").
Click on the Advanced tab and then go to the security section and make sure "SSL 2.0" and "SSL 3.0" are selected.
0x800A138F fix/resolution 4
Go to the Control Panel and open the Internet icon. (Or on the Tools menu in IE click "Internet Options").
Go to the "General" tab and click the languages button.
Make certain "English" is the first in the list.