You have:
<param name="host" value="$vboptions[ircroom]">
Should be:
<param name="command1" value="/join $vboptions[ircroom]">
I'm having one final issue. When your not logged in and a user selects to go to the chat, they are presented with the VB login screen, but on logging in users are forwarded to a 404 page (
http://www.domain.com/forum/chat/login.php) - is there a way they can be taken to the chat?
many thanks for a great hack!