I've had 6 or so people with this problem--I'll direct them to this thread and/or ask them to call you.
I've been freaking out over this for a solid hour or two, and I have the solution. I ALWAYS forget this, and I need to make sure I document it.
The problem lies with IE users who are accessing your site via poe-guild.com
Your address is loading the site in a frame, and IE takes a security issue with cookies from frames in other domain names.
Because you host your forums on the same domain name, the solution is to set up a redirect, where typing poe-guild.com redirects to poe.dkpsystem.com. If you're running php, you can do this easily in your index.php file of poe-guild.com to contain
<? header("Location:http://poe.dkpsystem.com") ?>Otherwise, you can do it in javascript:
<Script language=javascript>
location.href='http://poe.dkpsystem.com';
</script>