Hi Tobias,
Can you get us the permissions you had on the directory, especially the package cache? We should investigate this silent fail (well, not so silent eventually )
Some programs are able to somehow get windows to ask the user if it is okay to save files in certain folders. I haven't been able to figure out how to do this. For that and other reasons I went a different way but maybe you can figure out how to do this and solve the problem without having to change the folder structure.
Lou