When I view beta5 in IE, I don't see the users in the user box. If I click Hide Online Users Box, it goes away, and when I click Show Online Users Box it comes back, but still with no users in it. Also (minor nit), I'm not seeing the green circle at the end of the line when a chat message comes in.
It all works fine in FireFox.
EDIT: It looks like the problem is in the code that I got from Kerphi to turn the username into a hyperlink. If I comment out that code in customize.js then I see the user list again. Of course, I lose my links to the users' profiles. Something in beta5 must have changed to stop this from working. Kerphi, could you post the updated code I would need to do this?