If you want to try another avenue to get this working, you can download an IRC client and connect through that. My client of choice is HydraIRC. Make your user identity be your UStream user name. The URI for the chat server is IRC://chat1.ustream.tv and set your password as your UStream password. When you connect, type /join #day9tv and voila, the chat window will pop up.
That's mostly because of how old IRC is. All the clients have been in use for many many years, probably just receiving bug fixes and some features. The users are completely accustomed to it, so creating yet another IRC client or rehauling an existing one just doesn't sound like a good idea.
I'm a mIRC guy myself, but have you tried HydraIRC?
Another free and easy to use IRC client alternative:
If you don't want to install an application there is a number of "web irc client" like:
For Windows I've been using HydraIRC. Open-source, not GPL, but definitely a decent client for simple chatting.
I don't use irc for a whole lot anymore, but I'll come check out the new channel.