Did the “you do not have permission” message occur on the command line? If the user you login as on the server doesn’t own the files you will need to do the chmod-ing as root. If you don’t have root access, then I have no idea how you edited the files in the first place.
The plugin doesn’t do any checking to determine whether the files are writable. It probably fails quite horribly if you have set PHP to write errors to the screen.