MikTeX 2.8 Update Error "Windows API error 87"

This issue got once reported to the miktex-users mailing-list (Nabble archive: http://old.nabble.com/Problem-Updating-%28Windows-API-error-87%29-td24971196.html)

The final solution there was:

It turns out the problem was, I had an instance of MikTex open which was blocking the files needed for the install. After I closed the MikTex instance the install worked fine.

In general it is a good idea to close all application for updates under Windows. On failure reboot the machine and retry it again.

I had the same problem - the sollution above didn't work for me, but what worked can be found at http://comments.gmane.org/gmane.editors.lyx.general/69152. The sollution is:

Problem solved. PDFLatex doesn't die after a problematic run due to an uninstalled package. It was blocking some files which, I guess, needed to be modified by the Package Manager. After killing PDFLatex installation run smoothly.

Hope it helps!

I found that, for any "Windows API error 87" in MikTeX, deleting all the files in the following folder works.

C:\Users\%USER%\AppData\Local\MiKTeX\2.9\miktex\data\le

C:\ProgramData\MiKTeX\2.9\miktex\data\le