problems with sessions variables and virtual domains in apache

I have a windows 2000 server with apache 2.0 and php 5.1.2. I use session variables to validate users, each page have something like this: if($_SESSION["validated"]==0){ header("Location: index.php"); exit; } This worked fine when i had only one domain, but when i began to use virtual domains, sometimes, not always, the session variable lost the value or the session variable is distroyed, i don't know what really happens. I add this lines to httpd.conf for each domain and the main domain is first: <VirtualHost *:80> ServerAdmin admin@domain.com DocumentRoot "C:/Program Files/Apache Group/Apache2/htdocs/domain" ServerName www.domain.com ErrorLog logs/domain.com-error_log CustomLog logs/domain.com-access_log common php_admin_value upload_tmp_dir "C:/Program Files/Apache Group/Apache2/htdocs/domain/tmp" php_admin_value session.save_path "C:/Program Files/Apache Group/Apache2/htdocs/domain/session" </VirtualHost> At the beginning i didn't use the two last lines with php_admin_value, i add the lines for trying to solve the problem but it doesn't work. I have an application made with phpmaker and SquierreMail v.1.4.7 too, and i have the same problem in both. In both case sometimes, when i want to go to other page, the server ask me for the username and the password, it is not always. Please help me Thanks.