[Dan pinged me but I'm not a MS Engineer.]
@Steve only =>
What updates did you install last week?
Possibilities include KB2809289, KB2814124, KB2807986, KB2791765, KB2670838, IE10 plus a few updates for MS Office.
Note: KB2670838 is an IE10 Prerequisite Update. If KB2670838 wasn't already installed, it would have been "drive-by" installed when you installed IE10 (in which case KB2670838 prolly wouldn't be listed in
Installed Updates or Update History.
PS: Was IE10 Release Preview installed? Is Automatic Updates set to the Automatic configuration and if so, was IE10 installed via Automatic Updates?
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@Dan => To avoid confusion & duplication of effort, it would be best to post any/all further follow-up in replies to your own, new thread:
http://answers.microsoft.com/en-us/windows/forum/windows_7-windows_update/ms-update-fail-causes-api-ms-win-downlevel-user32/fc65057b-984f-40ef-bd6b-60666f9c7c6a
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For home users, no-charge support for security updates (only!) is available by calling 800-MICROSOFT (800-642-7676) in the US or 877-568-2495 in Canada. [1] [2]
For more information about how to contact your local Microsoft subsidiary [i.e., in other regions] for support issues relating to security updates, visit the following Microsoft International Support website:
http://support.microsoft.com/common/international.aspx?rdpath=4
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[1] Monday through Friday, 5:00 AM - 9:00 PM Pacific Time; Saturday and Sunday, 6:00 AM – 3:00 PM Pacific Time
[2] KB2670838 & IE10 are NOT security updates!