Are you able to do any kind of Survival Analysis? Meaning, what is the sequence of events they take in their journey clicking throughout the site, and perhaps even more importantly, at what point do they leave the session?
I'm thinking the latter might provide something useful:
1- they left immediately after posting. (they may be leaving to immediately cross post elsewhere)
2- they left after reviewing a non-Access thread (that may offend them in some way)
3- they left after reviewing a non-Access thread and then also participating in it (opposite conclusion as above)
4- they left after using the Search function without selecting a result (disappointed with its results)
5- they left after using the Search function AND spending time on a result (good utilization of site)
6- halfway through registration (they were frustrated with a process or content there)
7- they left after downloading a sample file left by a member (they got something useful & went on their way)
8- they left after visiting the Forums page, without doing anything else (didn't see the Category they wanted-i.e. Sharepoint, VBScript, SQL Server forum is dead)
9- they visited the site and quickly left by clicking on a signature link away rather than utilizing the site
10- they visited a specific forum and immediately left (Excel, SQL Server - may have concluded it's too inactive to bother posting for responses - I've done this a lot at various sites). I've always thought AWF might have twice the traffic if it could find a way to drive traffic to SQL Server forum--imagine just taking even a small amount of sqlservercentral's or stack overflow's market share on that!) Same with Excel: Many users think of Access help & Excel help in the same family of sites....anything we could do to up the ante on the Excel forum might be useful. So many Excel responses start with "I don't use Excel, but.....
One thing that I have always imagined is useful is something fast food chain surveys do a lot of. It's where a person selects what other restaurants they have visited in the past 30 days, and which 1 or 2 are their favorites, and whether they'd visit again in the next 30 days. (I guess in your case, though, there aren't all that many in the mix to begin with). You could leave it open free text so as not to provide too many ideas..
Just some thoughts I had.