I have no idea how or why folks are being denied access to the chat page specifically as there are no controls to limit access at that level.
Having said that, the chat room itself is hosted by Meebo and you can access it directly here: http://widget.meebo.com/mcr.swf?id=BtQnkZWkUY. It runs nicely in its own tab!
I'm wondering if the "Access Denied" message is actually being returned by Meebo or something. If someone could send me a screen shot of what they're seeing, that would help me figure it out.