$_SESSION is empty after setting values

Hey kids, i have a linux server with apache 2 and php running here. I can pass values from forms, and through the url to other php pages etc. My problem here is with SESSIONS. I create a session for a user when i have validated their login information, and send them a cookie and throw some junk in the $_SESSION[] variable. on the next page, the variable is empty however, $_SESSION["username"] is empty. all the values i set are empty. i checked the session storage folder, there is a file that is a session that has data in it matching what i told it to save, i checked the browser cookie, it exists, its session value matches that of the file, i dont understand why php seems to "forget" this info, or ignore the cookie...whatever it is its doing. I am hoping its a simple option i am missing somewhere. I hope one of you has an answer for me! i realllly need to get this website going. Thanks folks! --Dave