In the QV-installation where I had problem the source qvw is located on a fileshare on another server (same place where I want to create a folder)
That fileshare is mapped as Y: for both my user and the service-acocunt running the publisher-tasks.
The predefined variable $(QvWorkPath) returns the very same string both when running the qvw manually as well as with the publisher starting with Y:.
However that path with Y: can only be used when reloading manually, when running on the server I must use \\server\fileshare\.....
But now it works