Mark, as for your particular site. Did you make any changes to the URL or something. You have some very weird results in Google, and it's probably confusing them to say the least. I know you actually run under wikwirral.co.uk, however google is also indexing your site as cruisewirral.com. Now the problem is this.
Do this: site:cruisewirral.com +showflat
Now when you click on any of your search results you get sent to a page like this:
So it's being redirected, but that redirect link is bad. You have a couple thousand links in google under cruisewirral.com and they all end up just linking to the main forum page since it appears you have a bad redirect. I imagine Google would end up penalizing a site for that since they all just look like they are pointing to the same page.
