>
>Does someone have the ZIP file open in Windows Explorer? (it shows up in Explorer as "compressed folder" into which you are able to navigate as a normal folder)

No


>Have you checked on possibility of an antivirus blocking you? (e.g. you are updating ZIP file on network location, the moment you release access [i.e. close the file], host computer initiates an automatic scan -- blocking further updates until it finishes)
>If the file isn't local to the computer (i.e. it resides on network share), you're more likely to run into conflicts.

We are creating Zip file on local computer. Data is from local computer.


>Make sure you've got full access to the containing folder -- sometimes you get this effect if you've don't have sufficient rights to the folder in which the ZIP file is contained.

The containing folder shows 'Read only'. We we are able to do write operation from within the software as well as from explorer. The 'Read only' tag does not go.

Simple command like "pkzip a.zip a.bat" does not work (even at root directory)

Rakesh