Thank you for your post.
If you do not have full read/write privileges to the directory where the FileMaker Pro 6 database is hosted, then you will not have the ability to make changes to the file. In essence, it would be read/only. Just to make sure the file is not damaged, try moving the file to your local drive, open it, and see if you can make changes. If so, then you will need to fix permissions on the server.