About googlebot tracking location, it's normal that you only sees it on the index without the virtual folder option, it's only becasue in such case, the original code does not know the forum id, since only the topic one is available from the url, so the viewonline code will not be able to determine if a visitor is browsing a particular forum, and will use the index location instead.
So this does not mean that the google bot is not browsing threads or forums, and actually, we can tell he does since you have topics and forum cached already.
I still don't think that it will be easy to get the final clue on this one, since everything seems working ok on your site, but one thing is sure : Google is indexing your forum.
We today have 421 indexed pages on
http://www.google.com/search?q=site%3Aw ... 2Fforum%2F
and this is already almost doubling what we had 7 days ago.
Many things could have occurred, I even saw several time google all the sudden reusing very old version of the cache for my sites, with outdated urls in its results, like if some bad backup recovery had been involved after a server crash in DC or something like that.
It of course went back to normal pretty soon after, but it could only be google to have gone through an error.
The important sign is that it is actually indexing your forum so ...
++