[SOLVED] - SESSION: [function.serialize]: Node no longer exists

[eluser]mindprojects[/eluser]
Hi guys,i'm using CI 1.6.3 under XAMPP(win).I have this error about sessions,when i'm going back from a payment gateway.My app is running locally now.

Code:

A PHP Error was encountered

    Severity: Warning

    Message: serialize() [function.serialize]: Node no longer exists

    Filename: libraries/Session.php

    Line Number: 296

I found this:
http://ellislab.com/forums/viewthread/87609/
but couldn't help me.

My current config is:

$config['sess_cookie_name'] = 'ci_session';
$config['sess_expiration'] = 0;
$config['sess_encrypt_cookie'] = FALSE;
$config['sess_use_database'] = FALSE;
$config['sess_table_name'] = 'ci_sessions';
$config['sess_match_ip'] = FALSE;
$config['sess_match_useragent'] = FALSE;
$config['sess_time_to_update'] = 3000;

$config['cookie_prefix'] = "";
$config['cookie_domain'] = "";
$config['cookie_path'] = "/backoffice";

Any solution???Thanks