It seems I'm in trouble with my server. Most of my skripts which actually run fine for the last weeks don't work anymore. One of my problems is this here:
I have a User-section where I use sessions. It worked fine,the login-skript looks like this ( I got it from Kevin's tutorial "Managing user..." )

<?php
include("common.php");
include("db.php");
include("dologin.php3");

session_start();

if(!isset($uid)) {
?>

// html Form for user-registration


<?php
exit;
}

session_register("uid");
session_register("pwd");

dbConnect("xxx");
$sql = "SELECT * FROM veranstalter WHERE
userid = '$uid' AND password = '$pwd'";
$result = mysql_query($sql);

if (mysql_num_rows($result) == 0) {
session_unregister("uid");
session_unregister("pwd");

dologin ("Sorry, invalid password");

exit;
}

?>

And I put a :
include("login.php"); ?>
on the top of every skript in the user-area. This worked fine, but now I can log in the user-area, but when I click to the next page in the user section I see the form again to enter my username and password. So it seems that the sessions do not work. As I didn't change the skrip, and it worked fine until yesterday, it seems that some settings on the server changed. Is there any way the check up the settings or check if the session work ore whatever?