http://validator.w3.org/check?uri=http%3A%2F%2Fwww.hystersisters.com%2Fvb2%2F&charset=%28detect+automatically%29&doctype=Inline&group=0

One of these may be snagging Googlebot and causing him to head to the hills.

Also i don’t like your Robots.txt formatting, have a look here as an example of a really great vB robots.txt

http://forum.vbulletinsetup.com/robots.txt

If you correct these issues.

Also i would seriously think about adding /showpost.php to your Robots.txt

This is the individual post, and is really duplicate content of what’s in your thread. If every thread page has 20 posts, that means you have another 20 URL’s of that content, one new page for every reply with showpost.php

It’s far better to not waste the link equity on 20 pages, but rather have 20 times the authority being passed to your showthread.php page.

Also see what entering one of these showpost.php URL’s from the SERP’s is like:

http://www.hystersisters.com/vb2/showpost.php?p=6489&postcount=1

Not real good in getting visitors to your board is it? Most people don’t even know theres a link to the full version so read it and hit the back button.

You have 2.3 Million of these URL’s chewing up link authority.

Also i would seriously consider blocking calendar.php

There’s thousands of pages there that are all fairly duplicate chewing up link equity/authority.

Does your Calendar serve up content you want to rank for, and you want first time visitors from the SERP’s to land on? The answer is probably not.

The idea is not to have the biggest number of pages in Google, but to serve up the single best version of your content pages and have all your link authority going to these pages. As it is now it’s being spread to probably 3 Million other URL’s needlessly.

Also Google has a “Crawl Budget” where it assigns a crawl of “x” number of pages per day. Do you want Google his x number of pages for the next 3 days on your Calendar, or on your new posts and informative content?

Your problem is easily fixable, i’d like to write more but must head out shopping but this gives you something to go on.

But your communication will likely help many, many other webmasters with the information coming out of the dialogue.

(Following closely and waiting for “solution day” to arrive. All best!!)