logged

I formatted my machine a few days back. Since then I'm facing a weired problem. I've my mail account with rediffmail, after loging in when ever I'm clicking on any mail or any link in the mail box I'm getting logged out. It says "You have been logged out. Your session is invalid". I tried...

This is a rather wierd problem. I have WinXP Pro and ethernet based net connection. After enabling the local area connection and starting Firefox, I get a login page where I enter my username and password. After getting logged in, I get a page showing me details like hours used, MB's downloaded...