You can try using JPilot located at JPilot.com. For $50.00 its an amazing Java applet based on IRC chatting, and its very customizable, and customers seem to like it. You might want to check it out, or use the SEARCH function on these forums, this topic has been discussed before.
If it's ok with you to use an irc server, the jpilot applet would be a good choice. Then you could just have it on a single page, and manage your own banner ads within the page any way you wanted to. It's a very light applet too, so it loads fast, and it's pretty customizable. HTH
Well, it's a little bit different perhaps than you are used to. Nearly every hosting company will host a page containing the applet.
Just purchase the applet license, and set it up on that website space. Then you can have the applet connect to an irc server (which are almost always free) where you will setup a chat channel. Using the chat might be a little more 'cut and dry' than the system you currently use, but it's very scaleable.
Basically you'll pay monthly (or yearly) for website hosting,
Pay the onetime license fee for the applet,
Install the chat applet on a web page & configure it,
Setup your banner ads on the same webpage.
That's about all there is to it. There's quite a bit of info the the jpilot.com website too about using the applet, as well as some examples. I've setup a lot of these chats too if you need my help.