Hey there,
I am actually working with RaiderSoft on the login problem... should be fixed soon, but it you just refresh the page a few times when you have that problem you will get in.
As for performance, the chat hosting is done by RaiderSoft's machines and is very quick.
You can allow anyone access through several methods of authentication. For our site, you MUST enter the chat room through a specific page, and that page can only be accessed by registered members of our site.
You could easily create UBB.threads groups and have the chat link available only to them.
HTH,
Chris
