I think that you must either leave it open for guests or use some cloaking technique (check if an user has user agent set to googlebot and ip coming from google) to let googlebot spider your forum messages.
yes i have google bot and i set its permissions to member .. It has been 2 days or 3 searching in my forum but didnt find any of my topics while searching on google yet ..
Agree with daniel, if you have your forums close for guest, then google won't be able to index what it can't see. My forums are open for reading and closed for posting to registered only, that way G, Y! and MSN have indexed a lot of it, and I can leverage adsense to everyone. Low side is a lot of people does not register right away, they read for months and register only when they have a reason for posting. So, for having best of both worlds you could use the user agent technique, showing the content to bots and registered users only. I personally do not like forums which require registering for reading, so it's not an option I'd like to use.
Ups. posted right after you. Now that I read your answer to daniel, I think you have to be patience. The key in your position is to have links on other sites that are already indexed by SE pointing to your new forum, it takes about 1 week if you have those, and godknowhowlong if you don't and only suggest your domain using google's suggest URL page. Last domain I boght, took 5 days to be indexed after I placed a backlink on a PR4 website.
yes but I told you guys I set google bot setting to view forum as member not guest .. so it shall index my topics or not ? and how much time does it need to index ?