Session, cookie with IE6 in x64 system (strange problem)

[eluser]BDT[/eluser]
Hi all CI guru!

This is my first post in CI forum. First of all, sorry my bad english, but i have little english.

Previously, i make login system with authlib (from wiki), and works very well in Firefox, IE6, IE7.
But now, i installed WinXp x64 and when i want to continue my coding, i can't login.
I start FF and try to login: login successful.

On my laptop (windows xp 32 bit with ie6, ff) the login system works correctly.

After several debugging i found that in x64 IE6 cookie data not contain my variable none the less CI successfuly authenticating user and set my session cookie data with $this->CI->session->set_userdata()

I use this to set variable:

$UserParameterek = $this->CI->User_Model->GetLoggedInUserdata($user_id);
$UserParameterek['usr_logged_in'] = TRUE;
$this->CI->session->set_userdata($UserParameterek);
log_message('info', "Setting session parameters from authlib!");

Anyone have any idea for this problem?

supplement:
I load session library with CI autoload and i set the x64 IE6 Tools-Internet options->Privacy to "Accept All Cookies".