Files saved as not writeable

[knod]

I'm not sure that this is the place to write this issue, but the virtual box people say it's not a virtual box thing.

While working in mozart oz in virtual box, I save files to the folder shared with the host. When I try to re-open the file it opens as "not writeable" - it has been saved with read-only permissions for the virtual box. I have to go back to the host and change the permissions there to be able to edit the re-opened file. The user permissions in the host say the user can read and write, but the others show read only.

This is where I downloaded the image: http://sourceforge.net/projects/mozart-oz/files/Virtual%20Images/

Environment:
MacOSX Mavericks, 10.9.5
Macbook Pro

Let me know if there is any other information that would help.