I'm guessing that's your UAC kicking in if your screen goes blurry and darker behind the access denied alert ( if you're using either Vista or Windows 7 ) . If you still get access denied even when you've given the file permission to be accessed then you might need to turn UAC off temporarily ( in your User Account options ) to let you edit the file . You'd have to turn UAC off , reboot , edit your config file , turn UAC back on and then reboot again
