firefox 3 login problem with drupal 5

I think we all know about the login/cookie/session problem with firefox 3 on drupal.my

I was called to make the fix and here is the chronology of the event :

Platform : MS Windows XP Pro SP3
Browser : 1. Firefox 3 (3.0.1)
2. IE7

PART A

1. najibx installed drupal V 5 as an addon in his shared hosting account. Some basics and advanced module and themes was installed.
2. the site running well but encounter login problem with firefox 3 user.