The setcookie code above kills the cookie in all browsers including Opera.
Here is a demo made up with the code you now have. Login with username : demo password :demo
And as I am such a nice guy I have also zipped up all the files for you to download. Download all the files needed here (4k).
I hope you find this script useful. If you have any problems or have any suggestion then please use the webdevtips forums. Thanks