Session and MS-IE6

I verify users to my website with sessions. It's been working fine for the past couple of years, but recently I started having some problems using sessions for example: session_register("user_id"); if (!(user_id)){ .... and then I read the PHP manual and it suggested this instead: session_start(); if (!$_SESSION['user_id']){ .... which worked on my machine (Win98 and MS-IE5.5). But today I tried to login to my page from the client's computer using MS-IE 6 and I got the error: undefined index 'user-id'.... Does anybody know what's going on? Is there a bug with MS-IE6 when using sessions? I've read some of the other comments here about IE6 but they apply to forms, not sessions. Pance.