title: NSDictionary WriteToFile fails
body: <p>I can't work out why it keeps failing. It returns <code>NO</code>. I have searched this all afternoon, but nothing explains why or how to fix. Calling <code>[[NSFileManager defaultManager] isWritableFileAtPath:]</code> returns <code>NO</code>, which leads me to believe that the existing plist file can not be overwritten, but I can't work out how to change this.</p>