I had the same problem and suggestion #4 worked for me.
By the way, you can find related info at the troubleshooting site:
http://v4.windowsupdate.microsoft.com/troubleshoot/
Problem Description:
The error 0x800A138F is displayed when scanning for updates, but the Windows Update.log file will show error 0x800C0008.
Resolutions:
This is a generic error number which indicates a problem with the SSL connection with our server.
Some customers have resolved this issue by disabling or uninstalling internet acceleration software.
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Suggestion 2
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The error may occur because the language-setting in Internet Explorer is missing. To add a language, in Internet Explorer, select Tools-->Internet Options, and click the "Languages" button. Add a language to the list if empty.
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Suggestion 3
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Check the system time. SSL will not function if the system time is more than 100 days off.
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Suggestion 4
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Please uncheck "Check for server certificate revocation":
1. Open Internet Explorer
2. Click on Tools
3. Click on Internet Option from the drop down menu
4. Click on the Advanced tab
5. Scroll down to the Security Section
6. Unselect "Check for server certificate revocation"
7. Reboot the machine
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Suggestion 5
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One customer performed an MSN Messenger update, which fixed his 0x800c0008 Windows Update issue as well. Correlation not yet determined but an avenue to check if you have MSN Messenger installed.
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Issue Applies To:
Windows 2000
Windows XP