It turns out that the developer of the app had his zip app in a non-standard folder, and wrote the apps to look for it in the wrong place. So we users saw the error, yet he could not reproduce it. D'oh!

The solution:

Thanks to the work of fellow volunteer Ananas, we now have a work around solution for the people who can't get Windows work units to complete successfully with the "Can't open Zip Local File" error.

Using any compiled zip.exe from the http://www.willus.com/archive/zip64/ into a folder and extract it (the Win binaries package).
Copy the extracted zip.exe file to the WINDOWS folder/directory. This adds the zip fuction to the computers PATH statement, as Windows already is in the PATH you don't have to do anything else. No reboot required.
That is all there is to it.

Ananas has had heaps of successful work units and now I have my first successful works unit credited with points since May 2011.

(You could probably use any zip executable but this one we know works.)

(Still no word on the recalculated points for past Windows work units)

Conan