After installing Windows certificate update cannot login to Yahoo

Question

MS sent out a new "root certificate" update for Windows today. After installing it everything looks normal, but an attempt to login to Yahoo groups or mail fails with a "duplicate certificate number" error.
>>>>>>>>>>
Secure Connection Failed
An error occurred during a connection to login.yahoo.com.
You have received an invalid certificate. Please contact the server administrator or email correspondent and give them the following information:
Your certificate contains the same serial number as another certificate issued by the certificate authority. Please get a new certificate containing a unique serial number.
(Error code: sec_error_reused_issuer_and_serial)
* The page you are trying to view can not be shown because the authenticity of the received data could not be verified.
* Please contact the web site owners to inform them of this problem. Alternatively, use the command found in the help menu to report this broken site.
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I can login with no problems using IE7, which seems suspicious.

Answer 1

Hello,
Certain Firefox problems can be solved by performing a ''Clean reinstall''. This means you remove Firefox program files and then reinstall Firefox. Please follow these steps:
'''Note:''' You might want to print these steps or view them in another browser.
#Download the latest Desktop version of Firefox from http://www.mozilla.org and save the setup file to your computer.
#After the download finishes, close all Firefox windows (click Exit from the Firefox or File menu).
#Delete the Firefox installation folder, which is located in one of these locations, by default:
#*'''Windows:'''
#**C:\Program Files\Mozilla Firefox
#**C:\Program Files (x86)\Mozilla Firefox
#*'''Mac:''' Delete Firefox from the Applications folder.
#*'''Linux:''' If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see [[Installing Firefox on Linux]]. If you downloaded and installed the binary package from the [http://www.mozilla.org/firefox#desktop Firefox download page], simply remove the folder ''firefox'' in your home directory.
#Now, go ahead and reinstall Firefox:
##Double-click the downloaded installation file and go through the steps of the installation wizard.
##Once the wizard is finished, choose to directly open Firefox after clicking the Finish button.
More information about reinstalling Firefox can be found [[Troubleshoot and diagnose Firefox problems#w_5-reinstall-firefox|here]].
<b>WARNING:</b> Do not run Firefox's uninstaller or use a third party remover as part of this process, because that could permanently delete your Firefox data, including but not limited to, extensions, cache, cookies, bookmarks, personal settings and saved passwords. <u>These cannot be easily recovered unless they have been backed up to an external device!</u>
Please report back to say if this helped you!
Thank you.